May one eat biscuits, cakes and the like which have words/letters engraved on them?
To take a bite out from it: Some Poskim rule that even according to Admur 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 but not by breaking it and then placing it into ones mouth. However other Poskim rule that according to Admur they may not be broken even within the process of eating. According to this latter opinion, one may not give these such foods to children that have reached the age of Chinuch.
 Ketzos Hashulchan 144 footnote 3
 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.”; Teshuvaas Rama; Chok Yaakov 475; Levush
 Ra”sh Haleivi brought in Magen Avraham 340/6, although he himself concludes with Tzaruch Iyun; Mahril; M”B 340/15; SSH”K 11/8.
 Ketzos Hashulchan 144 footnote 3 [His final ruling is written on page 151 at the end of the paragraph]; Shabbos Kehalacha Volume 3 p. 369; 20/73
 The reason: The basis of this ruling is that a) There are Poskim [Degul Merivava] who always allow breaking letters within the process of eating [chewing it] and b) There are Poskim which allow even to break engraved letters. Thus, although Admur rules stringently on breaking within process of eating [with regards to letters written with icing] while the Magen Avraham leaves in question braking engraved letters, when both leniencies are combined, such as breaking within the process of eating letters engraved on a biscuit, one may be lenient. [Ketzos Hashulchan there] This seemingly holds true as well in accordance to the ruling of Admur in Hilchos Pesach [brought above] which simply forbids breaking the Matzah with engraved letters, implying that taking a bite from it is allowed. [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 to allow breaking them while eating remains the same.] See however the next 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 behind the leniency of engraved letters over external letters: Engraved letters are not common today, and thus since here one has no intent to write in the area that the letters are erased, and it is thus only a Rabbinical prohibition, in this case we allow it being that in non common cases the Sages did not make their decree. Hence here since engraving is uncommon they did not suspect that one may come to erase engraving with intent to write in its place. [Ketzos Hashulchan ibid]
 Rav Bitstritzky in Shut Ara Degalil p. 35; Piskeiy Teshuvos 340 that from Admur ibid it is implied that this too is forbidden; Rav Eliyahu Landa that the custom is to be careful not to eat such foods on Shabbos.
 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.