Sh'miras Shabas K'hilchasah (5739 edition), 8:1:
There's no prohibition of kneading [on the sabbath]… unless these three conditions are fulfilled:
- that he combine two distinct things
- that those things be small or viscous or, if they're naturally large, that they be ground or chopped
- that as a result of the kneading these things be mixed and attached to one another as a single mixture … even if there is no liquid in the two objects but they naturally stick, like mixing honey with soft cheese or butter with cocoa powder, which is also included in the prohibition of kneading
A very popular dessert/snack in Israel is מילקי. This is sold in individual-serving-size cups and comprises a whipped-cream-like substance (the top half, or so, of the cup) and what Americans call chocolate pudding (the bottom). There are various favored ways of eating this, depending on whom you ask; one of them is to mix the two parts together before eating. From the passage above, it would seem that that mixing would be forbidden on the sabbath. Does anyone know of an explicit ruling from a latter-day decisor about this snack specifically, or know of anything that distinguishes it from the general rule (or the honey-cheese case) in the passage above?