Preheat the oven to 400F (200C).

Make the fathead dough according to the separate recipe. If it's very sticky, add a little extra almond flour, then roll it out into a circle between two silicone mats.

Remove the top mat, and transfer the dough on the bottom mat to a baking sheet. Spread the ricotta onto the dough, leaving about an inch around the edge. Set aside.

Melt the butter in a pan, then add the mushrooms and onion powder. 

Continue to cook until the mushrooms are soft (about 10 minutes), then season with salt and pepper. Using a slotted spoon, transfer the mushrooms to the dough and spread them over the ricotta.

Add some fresh thyme leaves, then fold up the dough around the edges. Season with black pepper, then sprinkle some grated Parmesan over the top.

Bake for 15 minutes or until the crust is golden brown.