Heat olive oil on medium heat in a large skillet. Fry sage leaves until crispy, about 2 minutes per side. Remove sage from pan and place on a paper towel to drain.

Cook rigatoni according to package directions or until al dente. When pasta is done, reserve ¼ cup pasta water, then drain.

Meanwhile, in the same large skillet, cook Italian sausage for 4 minutes, or until it starts to brown.

Add mushrooms, red pepper flakes, salt, pepper, and garlic to the skillet. Cook for 5 minutes, until the mushrooms start to crisp.

Add white wine and butter to the pan. Simmer for 5 minutes, or until the wine is reduced. Add ¼ cup pasta water, and simmer until reduced.

Place rigatoni in a large serving bowl. Top with sausage and mushroom sauce, then top with crispy sage. Top with grated parmesan and serve.