Mocheik (Erasing) - Breaking Down the 39 Melachot

Are you allowed to break an Oreo cookie  on Shabbat, if you're going to be breaking   through the lettering that spells "Oreo?"  What if you have a cake that has " Happy   Birthday " written on it in icing? Are you allowed  to cut through the letters? One of the Melachot   of Shabbat is the Melacha of Mocheik, which means  erasing or destroying letters. And therefore,   when it comes to the icing on the cake, one should  not cut through any of the individual letters.   Rather, you should cut in between the letters  and only destroy the letters by eating them,   not with your hand or with a knife. When it  comes to the Oreo that's written in a cookie,   since the letters are part of the cookie, there's  no problem even breaking them with your hands.