Deep-dish delight: Chicago-style pizza at your fingertips
1 tablespoon unsalted butter
1 medium sweet onion, peeled and cut into 1-inch pieces
1 pound sweet Italian fennel sausage, removed from the casing
1 pound cremini mushrooms, cleaned and sliced into 1/8-inch pieces (about 5 cups)
For the sweet and spicy tomato sauce:
2 tablespoons olive oil
1 medium sweet onion, peeled and cut into 1-inch pieces
3 cloves fresh garlic, peeled and grated, any green centers discarded
Leaves of 1 small bunch fresh basil, finely minced
4 sprigs fresh oregano, stems and leaves
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