Boil a large pot of salted water, add spaghetti, and cook according to package instructions until al dente, about 8-10 minutes. Reserve a cup of pasta water before draining.

In a skillet, heat 1 tablespoon of olive oil over medium-high heat, add sliced button and oyster mushrooms, and sauté until golden brown and tender, about 3-4 minutes.

Reduce heat, add the remaining tablespoon of olive oil, then stir in finely chopped garlic, cooking for 2-3 minutes until light golden.

Sprinkle chili flakes into the garlic and oil mixture, add reserved pasta water, season with salt, and let simmer for 2-3 minutes.

Add the cooked spaghetti and sautéed mushrooms to the skillet, tossing until well combined, about 2 minutes.

Stir in parsley, serve hot topped with grated Parmesan if desired.