Cook pasta-of-choice following package directions. Reserve ¾ cup of the pasta water before draining in a colander, then drain and set aside.
Meanwhile, heat olive oil and butter over medium heat in a large skillet. Add onions and cook, for 3-5 minutes until beginning to soften. Then, add in mushrooms and cook until all their water has been released and evaporated, about 7-10 minutes.
Add the garlic continue to cook for 1 minute, or just until the garlic softens.
Add in red pepper flakes, salt, pepper, and thyme to your mushroom mixture and stir to combine.
Add ¼ cup of the reserved pasta water to the skillet and stir to combine, then add in your ricotta cheese. Add more reserved pasta as desired. I usually find ¼ cup to be enough. Discard remaining if you don't use.
Add in pasta and stir until everything is evenly combined, adding in more pasta water as necessary. Taste and adjust seasoning.
Garnish with fresh chopped parsley, and the additional ricotta on top of the pasta if desired. Add a pinch of additional red pepper flakes, if desired, and serve.
