That sounds like a delicious, quick, and elegant solution! With just 1 cup of milk and 2 apples, prepared in minutes, it sounds very much like a quick soufflé, casserole, or a light crêpe batter made in a blender, then topped or filled with apples.
The most likely candidate for a light and fluffy French dessert that meets these criteria and takes little time is clafoutis, or a lightning-fast version of crème brûlée/pâtissière with apple.
I suspect you mean a quick apple and milk casserole or a kind of “magic clafoutis” (a thin, baked pancake batter around the apples).
Would you like the recipe for this quick, light apple and milk casserole that only takes a few minutes to prepare and then goes in the oven?