Cook the penne pasta according to package instructions until al dente. Drain and set aside.
In a large skillet, heat 1 tablespoon of olive oil over medium heat. Add the sliced mushrooms and cook for 5-7 minutes, until they are tender and browned. Remove from the skillet and set aside.
In the same skillet, add the spinach leaves and cook for 2-3 minutes, until they are wilted. Remove from the skillet and set aside.
In a food processor, combine the pine nuts, garlic, and Parmesan cheese. Pulse until the mixture is finely chopped.
Add the cooked mushrooms and spinach to the food processor and pulse until everything is well combined.
With the food processor running, slowly pour in the olive oil until the pesto is smooth and creamy. Season with salt and pepper to taste.
Toss the cooked penne pasta with the mushroom and spinach pesto until it is well coated.
Serve the pasta hot, topped with additional Parmesan cheese if desired. Enjoy!