Boil a large pot of water. Add a generous pinch of salt and cook the tortellini just to al dente, according to package instructions. Drain and set aside.
18 ounces fresh tortellini
While the pasta cooks, add 2 Tablespoons of the butter and 1 Tablespoon olive oil to a large skillet set over medium-high heat. When the butter is melted, add the mushrooms. Sauté for about 5 minutes, stirring occasionally, until the mushrooms are nicely browned. Add garlic and cook for another 30-60 seconds, just until fragrant.
4 Tablespoons butter, 1 Tablespoon olive oil, 12 ounces sliced mushrooms, 2 cloves garlic
Reduce heat to medium-low, then add the remaining 2 Tablespoons butter to the skillet. Let melt, then stir in the drained tortellini and Parmesan. Season with salt and pepper to taste. (I usually add 1/2 teaspoon salt and 1/8 teaspoon pepper, but this will vary according to taste.) Sprinkle with parsley, serve, and enjoy!
3/4 cup freshly-grated Parmesan cheese, 1-2 Tablespoons chopped fresh parsley, kosher salt and black pepper