Bring a large pot of salted water to a boil. Add your pasta and cook until al dente, about 8-10 minutes. Drain and set aside.
While the pasta cooks, heat a large skillet over medium heat and add a tablespoon of olive oil. Once shimmering, add the sliced mushrooms and cook, stirring occasionally, until deeply golden and fragrant, about 8 minutes.
Push the mushrooms to the side of the pan. Add chopped onion and minced garlic to the cleared space. Cook, stirring often, until the onion is translucent and sweet, about 3 minutes.
Sprinkle the flour or arrowroot powder over the mushroom mixture and stir well to incorporate, cooking for about 1 minute. This helps thicken the sauce later.
Gradually pour in the vegetable broth, stirring constantly to prevent lumps. Bring the mixture to a gentle simmer and cook until slightly thickened, about 3-5 minutes.
Stir in the plant-based sour cream and smoked paprika. Mix until the sauce is smooth and creamy, then let it simmer gently for another 2-3 minutes. Season with salt and pepper to taste.
Add the drained pasta to the skillet and toss to coat evenly with the mushroom sauce. Cook together for 1-2 minutes so flavors meld and the pasta warms through.
Remove from heat and let sit for a minute. Serve hot, garnished with fresh herbs if desired. Enjoy this comforting, plant-based take on stroganoff!
