Bring water to a boil and cook the pasta until al dente, for about 10 minutes or according to package directions. Drain the pasta, reserving about a 1/2 cup of the pasta water. Set aside.
Meanwhile, heat 1 tablespoon olive oil in a large high-sided skillet or Dutch oven over medium high heat. Add the ground turkey breast and cook for about 5 minutes, breaking up the turkey meat. Add the onions and mushrooms and cook, stirring often, for about 7 to 8 minutes.
Add the spinach, garlic and cooked pasta into the saucepan and toss to combine and let the spinach wilt, for about 2 to 3 minutes. Pour in some of the reserved pasta water (start with just a 1/4 cup) if you need to loosen up the pasta. You may not need to add the pasta water. Season with salt, pepper, and the red pepper flakes if using. Serve immediately and garnish with the freshly grated Parmesan cheeses and the parsley. Enjoy!