Put olive oil in hot pan, add sausage and brown, breaking up meat with spoon, remove and strain excess fat and reserve.
In same pan add onions and peppers and garlic saute` until slightly browned. Return sausage to pan, add crushed tomatoes, and oregano, simmer 15 minutes, add salt and pepper to taste.
Polenta Preparation:
In a deep pot, bring liquid to a boil. Slowly whisk in polenta, lower heat and let simmer for 30 minutes, stirring frequently with wooden spoon.
When cooked, stir in parmigiano, and butter. Salt and pepper to taste.
Then pour hot polenta into ½ sheet pan, smoothing with a rubber spatula.
Place in refrigerator and let firm up completely.
Assembly:
Spoon and spread thin layer of sauce evenly over cooled and firm polenta in same sheet pan.
Top with mozzarella and parmigiano and drizzle of olive oil.
Bake in oven at 400F until cheese is melted and starts to bubble. Let it cool for 5 minutes and slice like pizza