Start by bringing a large pot of salted water to a boil. While that’s heating up, go ahead and dice your tomatoes and slice your mushrooms.
Once your water is boiling, add your penne pasta and cook according to package instructions until al dente. While the pasta cooks, heat olive oil in a large pan over medium heat.
Add the sliced mushrooms and sauté until they soften and release their moisture. Stir them around and let them get lightly golden. Add your crushed red pepper flakes. Remember — half a teaspoon for mild, one teaspoon if you like a little kick.
Once the pasta is done, drain it and transfer it directly into the mushroom pan. Add the diced tomatoes and stir everything together.
Toss in the fresh spinach. It’s going to look like a lot — almost like a salad. That’s okay. Keep stirring. It will shrink down as it wilts. Turn the heat up slightly and stir until the spinach softens and everything starts coming together.
Pour in the heavy cream and stir until the sauce becomes creamy and coats the pasta evenly. Season with salt and black pepper to taste.
Sprinkle in the Parmesan cheese and give it one final stir. Top with extra Parmesan and serve immediately.
