Puffed and golden and impressive, this pot pie is one of the heartiest and most satisfying vegetarian main dishes there ever was. Instead of classic pot pie filling, typically meat-heavy and thickly sauced, this one is packed with vegetables. Roasting the mushrooms and onions give it an extra layer of flavor, and the shingled puff pastry is just plain fun (plus you don’t have to make your own dough or crimp any edges).
Some logistics: you can make the filling up to a few days in advance and refrigerate it; or you could lay the puff pastry on the skillet up to a day in advance, refrigerate it, and then brush with the egg right before baking. A combination of creminis and shiitakes is great here, but feel free to use whatever mushrooms you can find and enjoy.