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8. Removing the fat off from the surface of milk and all cases of the like such as removing dirt from food:
If one desires the milk and not the fat: As was explained in the previous Halacha with regards to pouring out unwanted liquid from a food, similarly it is permitted to gather [some of] the fat which floats on the surface of milk (called cream) and when one reaches near the actual milk, he is to leave some of the fat still [on the surface] together with the milk. [See Q&A]
If one desires to eat the fat right away: [However] if one wants to eat the [fat] right away, then [it is permitted to remove all the fat and] he does not need to have remain any [of the fat] together with the milk.
The reason for this is: because it is permitted to separate food or liquid from amongst the residue in any case that one plans to eat or drink it right away so long as he does not separate it through using a vessel but rather does so with his hands as was explained [above in Halacha 4]. [See Q&A]
Ruling of Siddur-Removing fat together with some liquid: Regarding fat that floats on the surface of the gravy, one may not throw it out through a spoon taking with it some of the liquid as this is similar to removing waste from food which one is liable on.
Summary: Gathering the top layer off the surface of a food in order to eat that layer:
To remove fat that is on the surface of milk is permitted to be done to eat anytime on Shabbos [whether one plans to eat the fat on Shabbos or to eat the milk under the fat] up to the area of the surface that is in direct contact with the milk/food under it. The area of fat however that is in direct contact with the milk has all the separating prohibitions and thus may only be removed to be eaten right away.
How much fat is one required to leave upon the surface when removing the fat due to desiring only the milk?
It is not enough to simply leave a mere sliver of fat which in any case would be very difficult to actually separate from the milk [without taking the milk with it], rather one must leave over a recognizable amount, enough of an amount that it could technically be easily removed from the milk.
May one remove the entire fat together with some of the milk if he desires to get rid of the fat and drink the milk?
According to the opinion of Admur in the Siddur this is forbidden to be done.
May one use a spoon to remove the fat?
Whatever amount of fat is permitted to be removed [dependent on whether one desires the fat or the milk] may be removed with a spoon, as explained above in Halacha 4 Q&A that using a spoon is equivalent to using one’s hands.
May one remove dirt/waste from the surface of a food, such as on top of cream cheese and the like?
Doing so is only permitted through pouring out the dirt together with some of the cheese.
May one remove whip cream from on top of pudding?
The area of cream that is in direct contact with the milk has all the separating prohibitions applicable and thus may only be removed to be eaten right away.
 Admur 319:18; M”A 510:13; M”B 319:62
 The term used by Admur seems to imply it is permitted to gather using a spoon.
 Upon standing for 12 to 24 hours, fresh milk has a tendency to separate into a high-fat cream layer on top of a larger, low-fat milk layer. The cream is often sold as a separate product with its own uses; today the separation of the cream from the milk is usually accomplished rapidly in centrifugal cream. The fat globules rise to the top of a container of milk because fat is less dense than water.
 According to Admur above in the previous Halacha one must leave some of the fat together with the milk even if he plans to immediately drink the milk and this is not similar to the peeling of a fruit which is allowed to be done prior to eating it. [This opposes the opinion of the Igleiy Tal which allows one to remove it immediately prior to eating it.] See Shabbos Kehalacha Vol. 2 p. 237
 Admur 319:18
 This applies even according to the Siddur being that here we are not discussing pouring the fat out but rather gathering it with ones hand and the like, of which the Siddur never argued on.
 Shabbos Kehalacha Vol. 2 p. 236
 So rules the Ketzos Hashulchan [125 footnote 24] with regards to how much fat one is allowed to pour out of the dish. The same thus applies here when removing fat from the surface.
 Shabbos Kehalacha Vol. 2 p. 237
 As rules Admur regarding removing the fly together with some of the liquid. [See Ketzos Hashulchan 125 footnote 24]
However the M”B rules that this is allowed.
 Ketzos Hashulchan 125 footnote 24; Chayeh Adam in Nishmas Ada, 82:2; Shabbos Kehalacha Vol. 2 p. 236
 So rules the Ketzos Hashulchan 125 footnote 24 based on an inference from the Alter Rebbe in the Shulchan Aruch on the word “Liklot” that he uses.
Opinion of M”B: In 319:62 the M”B rules a spoon may not be used to gather the fat above milk even if one plans to eat it immediately. In Shaar Hatziyon 319:58 he explains this to also be the opinion of Admur. However, in 319:66 he contradicts himself and rules a spoon may be used. The Chazon Ish answers this by saying the case of cream on top of milk was an exception being that the spoon helps for the actual separation, while in 66 it is allowed as it is used simply so one does not dirty himself. So, concludes also Minchas Yitzchak 1:76. See Shabbos Kehalacha P. 148-149
 This applies even according to the Siddur being that here we are not discussing pouring the fat out but rather gathering it with one’s hand and the like, of which the Siddur never argued on.