Set oven to 350 degrees.
In a large skillet cook the sausage meat with onion, bell pepper and garlic until browned, stirring to break up the meat; drain fat and set aside.
Grease a 14-inch round deep-dish pizza pan then dust lightly with flour.
In a medium bowl mix together the flour with baking powder, salt, Italian seasoning, black pepper and cayenne pepper (if using) add in milk and eggs, stir until well blended.
Pour the mixture into the prepared pan tilting pan as necessary so that the batter covers the bottom of the pan.
Sprinkle the top of the batter with 1/4 cup parmesan cheese, then sprinkle the sausage mixture and sliced mushrooms over the batter and cheese.
Bake at 350 degrees for about 25-30 minutes or until pizza is golden brown.
Remove from oven and drizzle with pizza sauce, then 1/4 cup grated parmesan cheese and then top with grated mozza cheese; return to oven and bake about 8 minutes or until the crust is a deep golden brown and the cheese is melted.