Get all the prep done before you start cooking: mince the garlic and finely chop the onion. Thinly slice the cremini mushrooms and chop the parsley.

Cook the pasta in a large pot of generously salted boiling water, until al dente. Drain, reserving ½ cup of the cooking water.

In a large skillet, heat 1 tbsp olive oil over high. Add mushrooms, cook until they start to release moisture, for 4-5 minutes, stirring occasionally. Add 1 tbsp butter, stir until it melts and cook until mushrooms are golden brown and crispy. Lower the heat, add garlic and onion, cook for 3 minutes. Season with salt and pepper. Stir in the parsley and remove the mushrooms from skillet.

In the same skillet, heat 1 tbsp olive oil over medium-low. Add pepper and red pepper flakes. Cook, stirring, until toasted, about 1 minute. Add the remaining butter and stir until melted.

Add cooked tagliatelle and ¼ cup reserved cooking water to skillet and toss to combine. Turn off the heat and add Parmesan. Stir and toss until melted and the sauce coats the pasta. Add more pasta water if the pasta looks too dry. Add mushrooms and stir until combined. Adjust salt to your own taste.

Transfer pasta to bowls and serve immediately. Serve with grated Parmesan and extra red pepper flakes. Enjoy!