The name mille-feuille translates to "a thousand leaves" and often refers to almost any French dessert made with puff pastry. You can buy frozen puff pastry in the frozen foods section of most grocery stores. A simple Napoleon can be made by cutting the puff pastry (thawed in the frigerator first)into rectangle shapes, filled with a layer of jam, a layer of pastry cream, and/or a layer of whipped cream, then topped off with a chocolate coating.
There are many puff pastry desserts that can easily be made at home. I hope this helps. Happy Baking, Chef Joy L.