Bring a pot of water to a boil with a large pinch of salt. Halve, peel, and thinly slice the onion. Remove ribs and stems from the chard and thinly slice. Slice the chard leaves into ribbons. Mince or grate the garlic.

Add the swiss chard stems to the boiling water. Cook for 2 minutes, then add the leaves to the pot. Cook for about one minute until wilted. Remove with a slotted spoon and set aside. Keep the pot on the stove , we'll be using it for the pasta.

Heat 1 tablespoon olive oil in a non-stick pan over medium heat. Add the onion and season with salt and pepper. Cook for about 5 minutes, until slightly softened.

While the onions cook, add the pasta to the boiling water and cook for 9-10 minutes, until al dente.

Meanwhile, add the mushrooms to the pan with the onions and season with salt and pepper. Cook, tossing, for about 5 minutes, until slightly golden brown. Add the garlic, paprika, and as many chili flakes as you dare. Cook for 30 seconds, until fragrant.

Add the sour cream and and 1/4 cup of pasta water to the pan. Stir to combine. Cook until slightly thickened, about 2 minutes.

Drain the pasta and add it to the pan with the sauce. Add the chard stems and leaves and toss to combine.

Serve the pasta with a sprinkle of parmesan cheese on top!