Provençal Upside-Down Omelet with Mushrooms, Croutons, and Lardons

Please note: This is not the type of French fold-over omelet with a runny interior that we normally associate with the word. Rather, a Provençal omelet is firm like a frittata. It’s also different in that it’s as good cold as warm and is thus ideal for a picnic.

The mushroom filling for this delicious omelet recipe is best prepared in a clay pot with a glazed interior, such as a Chinese sandpot or other small casserole with cover. The mushrooms are wrapped in parchment and placed in