Bring medium sauce pot of water to a boil for the pasta, add ½ teaspoon of salt. Cook until al dente according to the package instructions.
Add olive oil and butter to skillet or cast iron pan, then add mushroom and sauté until golden and caramelized, turning over once halfway through, about 6-7 minutes. Add onions and sauté for another 3 minutes, then add garlic and cook for another minute. Stir in paprika, pepper and flour, combine well. Pour in the vegetable broth and simmer for about 3-4 minutes, until it starts to thicken.
Once the sauce has thickened, add the reserved pasta water and spinach, simmer for a minute until spinach is wilted. Add the sour cream in a small bowl and take some of the sauce and stir it in with the sour cream. You don't want the sour cream to be cold when adding it to the skillet as it may curdle.
On low-medium heat, add the sour cream mixture and mix it in thoroughly. Allow to simmer for about a minute. Stir in the pasta and coat well with the sauce.
Garnish with parsley. Enjoy!
