May one eat biscuits, cakes, candies, chocolate, and the like, which have words/letters/pictures engraved on them?
To break it and then eat it: It is forbidden to break the letters that are on a food, even if the letters are engraved. Accordingly, one may not break a piece off from the cake or biscuit if doing so entails breaking one of the letters.
To take a bite out from it: Some Poskim rule that one may break engraved letters within the process of eating. Meaning, that one may break the letters in the process of taking a bite from the food, and the prohibition is only against breaking it with one’s hands and then placing it into one’s mouth. However, other Poskim rule they may not be broken even within the process of eating. According to this latter opinion, one may not give such foods to children that have reached the age of Chinuch. Practically, one is to speak to his Rav for a final ruling.
Engraved pictures: Pictures and designs that are engraved onto a cake, biscuit and the like, may be eaten as normal on Shabbos. One may even break a piece off and eat it, so long as there are no letters on the cake.
One may not break the engraved letters found on a food, although some are lenient to do so in the process of eating, through taking a bite, as opposed to breaking a piece off with one’s hands. One may break the engraved picture of a food even with one’s hands.
May one dip a biscuit with engraved letters into a tea?
One may dip a biscuit that contains engraved letters into tea if doing so will not inevitably cause the biscuit to break in the area of the letters. If, however, the biscuit will break in the area of the letters then doing so is forbidden. [One must beware to wash his hands without a blessing prior to eating biscuits dipped in coffee or tea and the like, prior to eating them.]
May one make cheese cake using whole biscuits that contain engraved words?
It is not advised to do so due to the eating restriction to be explained. If one did so, then care must be taken not to break the biscuits in a way that the letters will break. According to some Poskim, however, one may eat the biscuits whole, having them break in his mouth.
 Ketzos Hashulchan 144 footnote 3
 Admur 458:8 “The symbols which are made on the Matzos should not be made through forms of letters using a molded imprint [i.e. cookie cutter], or with one’s hands (for the reason explained in chapter 470 and others) being that one is required to break them on Yom Tov, and there are opinions who prohibit to break a cake which has forms of letters on it even though he does not intend to erase the letters, but rather to eat them on Yom Tov, as was explained in chapter 340. Rather these symbols are to be made through holes or grooves, as long as one is careful to extremely speed their process, as was explained in chapter 460, see there.”; Implication of Admur 519:6 regarding a Chosem; Teshuvas Rama 119; Chok Yaakov 475; Levush 473; M”B 475:57; Chazon Ish 61:1; Magen Avraham 340:6 leaves this matter with a Tzaruch Iyun; Kaf Hachaim 340:31 “One who is stringent is blessed”; Bris Olam Mocheik 4; Shevet Halevi 9:77 “Proper for each person to be stringent”;
Other opinions: Some Poskim rule the erasing prohibition does not apply to the engraved letters that are on a food. [Ra”sh Halevy brought in Magen Avraham 340:6, although he himself concludes with Tzaruch Iyun; Maharil; Degul Merivava 340; M”B 340:15 [in contradiction of 475:57; See Piskeiy Teshuvos 340 footnote 65]; Har Tzevi 214; SSH”K 11:8 footnote 31 in name of Rav SZ”A]
 The reason: It is Rabbinically forbidden to erase letters on Shabbos even if one does not plan to write any letters in its place. [Admur 340:4]
 Ketzos Hashulchan 144 footnote 3 [His final ruling is written on page 151 at the end of the paragraph]; Shabbos Kehalacha Volume 3 20:74 [p. 369]; [To note that the Ketzos Hashulchan did not mention this ruling in chapter 144 and only later was it mentioned by him in the glosses to the end of the 7th volume, nevertheless, it is implied from there that his conclusion is to allow breaking the letters in the process of eating. See however the case of a bottle cap with engraved letters that the Ketzos Hashulchan allows one to break it on Shabbos, although contradicts himself in the glosses to the end of volume 7. Vetzaruch Iyun. The Rebbe was once addressed this question of whether one may break engraved letters according to Admur, and the Rebbe answered that no conclusive stance can be taken on this issue. Vetzaruch Iyun, being that this matter is explicitly ruled on in Admur 458:8]
 The reason: The basis of this ruling is that a) There are Poskim [Degul Merivava 340; M”B 340:15] who always allow breaking all letters within the process of eating [chewing it] and b) There are Poskim [See Poskim ibid in other opinions] who allow breaking engraved letters even with one’s hands. Thus, although Admur rules stringently regarding on breaking within process of eating [with regards to letters written with icing], while the Magen Avraham leaves in question regarding breaking engraved letters, when both leniencies are combined, such as breaking engraved letters of a biscuit within the process of eating, then one may be lenient. [Ketzos Hashulchan ibid] This seemingly holds true as well in accordance to the ruling of Admur in Hilchos Pesach 458:8, as there he writes that a) some opinions rule and b) it is forbidden to break the Matzah with engraved letters. This implied that taking a bite from it is allowed, as in such a case there are two reasons to assume the Sages would not make a decree, and one may rely on those opinions who argue on the “some opinions rule”. Likewise, we similarly see in Admur 460:9 in which he implies that it is permitted to break Matzos that contain engraved pictures. So is also the implied ruling of M”A 340:6 as he understood from the Mordechai [see Ketzos Hashulchan ibid] Now, in truth, pictures have the same status as letters regarding writing and erasing on Shabbos, as rules Admur 340:10, rather one must say that the Rabbinical decree against erasing was not made in all cases, and so too here, since there are two reasons to be lenient, it is permitted to be done.
The reason behind the leniency of engraved letters over external letters: The above allowance only applies to engraved letters, while external letters are prohibited to be broken even within the midst of eating. [Admur 343:10] Vetzaruch Iyun as why by engraved letters we are more lenient, as engraving is also prohibited due to writing. Some Poskim suggest that engraving letters is no longer common today, and thus, since one has no intent to write in the area that the letters are erased, in which case it is at the very most only a Rabbinical prohibition, therefore, the Sages did not make their decree, as they do not decree against uncommon cases, if it will prevent Oneg Shabbos. Now, although we see that Admur ibid and other Poskim ibid were stringent even regarding erasing engraved letters on foods, nonetheless, one can suggest that they did not extend the prohibition to a case of breaking them within the process of eating, in contrast to external letters, which Admur forbids breaking even within the process of eating. [Ketzos Hashulchan 144 footnote 3]
Ruling of Admur in 519:6: In Admur 519:6 he rules that one may not open a Chosem on Shabbos if it contains letters or pictures. This implies that it is forbidden to break engraved pictures, just as engraved letters. However, in truth, as the Ketzos Hashulchan ibid states, the above allowance was only given to food, for the sake of Oneg Shabbos, and not towards other cases.
 Rav Bistritzky in Shut Ara Degalil p. 35; Piskeiy Teshuvos 340:6 that from Admur ibid it is implied that this too is forbidden; Rav Eliyahu Landau that the custom is to be careful not to eat such foods on Shabbos; See article of Rav Shalom Dovber Hertzel in Koveitz Oholei Torah 1083 p. 108 [Rav Bistritzky does not make mention of the ruling of the Ketzos Hashulchan throughout his entire ruling. However, at the end in a footnote he mentions that he found a ruling of the Ketzos Hashulchan which contradicts his ruling, and he writes that seemingly the Ketzos Hashulchan forgot the ruling of Admur in 458:8. However, in truth the Ketzos Hashulchan in his Hosafos does add the ruling of Admur there and nevertheless does not retract his final ruling said above.]
 Implication of Admur 460:9; Beis Yosef 460 in name of Rabbeinu Yerucham; M”A 340:6 in his understanding of Mordechai; Ketzos Hashulchan 144 footnote 3; Shabbos Kehalacha vol. 3 20:75; See Piskeiy Teshuvos 340 footnote 66; Mishnas Yosef 7:80; Orchos Shabbos 15 footnote 36 in name of Rav Gerelitz and Rav Chaim Kanievsy]
 The reason: It is unclear as to why Admur, and the Poskim ibid, are more lenient by engraved pictures than engraved letters, if they both are part of the same writing and erasing prohibition. However, perhaps the Sages did not apply their decree against erasing an engraved picture in such a situation, being it is not as common as erasing an engraved letter. [See Ketzos Hashulchan ibid] Alternatively, perhaps, since erasing a picture is only a Tolda of writing, therefore the sages were more lenient. [Shabbos Kehalacha ibid footnote 185; Rav SD”B Levin in Koveitz Oholei Torah 797 p. 43] Alternatively, some suggest that there is no writing or erasing prohibition involved in engraved pictures [See Tehilah Ledavid 340:3 in his initial understanding of Rambam-See Koveitz Oholei Torah 1083 p. 108] Now, although Admur 340:6 explicitly rules that one may not engrave into ash, perhaps that refers only to letters and not pictures. Now, although the Poskim do not differentiate between pictures and letters and rather rule that making a drawing is a Tolda of writing [See Admur 340:10; M”A 340:6; Rambam Shabbos 11:17; Degul Merivava 340; Tehilah Ledavid 340:3] perhaps Admur holds that when it comes to pictures, there is a difference between writing and engraving. See Admur 340:10 who writes “One who makes marks and designs on a document and the like, in the way that the artists design, is liable due to an offshoot of the writing prohibition. The same applies for one who erases it.” Admur does not simply write that pictures have the same status as writing, and qualifies the case with “on a document..in the way that artists design..” This extra wording of Admur seems to imply that there are cases that the writing prohibition does not apply to making a picture, and perhaps an engraved drawing is one of those cases. See also Admur 302:5 who writes “For example one who designs a [picture of a] figure on a vessel which is waiting to be designed on, even if he only designed part of the figure, he has done part of the finishing touch of the vessel and is liable [for a sin offering]. As although the figure on its own is not considered a [Biblically] forbidden form of work, nevertheless now that the vessel is complete and fixed through his action it is considered [a Biblically forbidden form of] work.” If the above is correct, then there would be no prohibition to engrave pictures into non-Muktzah sand, a cake and the like. Vetzaruch Iyun, as I have not found any Poskim who suggest such a ruling.
 Admur 458:8 regarding Matzah on Pesach
Other opinions: Some Poskim allow breaking engraved letters that is on food. [M”B 340:15; SSH”K 11:8. Ra”sh Halevy brought in Magen Avraham, although he himself concludes with Tzaruch Iyun]
 Ketzos Hashulchan 144 footnote 3; Shabbos Kehalacha Volume 3 p. 369; 20:73