Simple Sausage and Mushroom Ragu

1. In a saute pan, heat the olive oil over medium high heat. Add the onion and cook until soft and golden brown, about 3 minutes. Add the sausage and mushrooms and cook, draining the excess fat if necessary, until the sausage is very browned and somewhat crispy, about 10 minutes.
2. Add in the milk, chicken stock, tomato paste and salt and pepper, to taste, and reduce heat to a simmer. Cook for 15 minutes.
3. Serve over cooked pasta (I like rigatoni). Sprinkle with grated Parmesan.

Adapted from Mario Batali.