Garlic-cremini pasta

Pasta, orecchiette	12 ounces
Oil, olive	¼ cup
Mushrooms, cremini, sliced	1 pound
Garlic, minced	5 cloves
Butter, unsalted	4 tablespoons
Parsley, chopped	¼ cup
Salt
Pepper, freshly ground
Parmesan

1. Boil the pasta, drain well, and reserve ½ cup of the water. 
2. In a skillet, heat oil over moderate heat. 
3. Add the mushrooms and garlic; cook until golden, about 8 minutes. 
4. Stir in the pasta, reserved pasta water, butter, and parsley. 
5. Cook, tossing, for 2 minutes. 
6. Season with salt and pepper, sprinkle with parmesan.