Bring a large pot of salted water to a boil and cook the pasta until al dente, about 8-10 minutes. Drain and set aside.
While the pasta cooks, clean and slice the mushrooms into even pieces for uniform browning.
Heat the olive oil in a large skillet over medium heat. Add the sliced mushrooms and cook, stirring occasionally, until they release their juices and turn golden brown, about 8 minutes. You should hear a gentle sizzling and see the mushrooms becoming caramelized at the edges.
Add the finely chopped onion and minced garlic to the skillet with the mushrooms. Sauté until fragrant and the onion becomes translucent, about 3-4 minutes. The mixture should smell warm and earthy, with a slight sizzle.
Stir in the smoked paprika and season with a pinch of salt and pepper. Cook for another 30 seconds until the paprika releases its smoky aroma, coating the mushrooms and onions evenly.
Pour in the vegetable broth and bring the mixture to a gentle simmer. Allow it to cook for 4-5 minutes, reducing slightly and thickening the sauce. You'll notice the mixture bubbling gently with a rich, earthy scent filling the air.
Reduce the heat to low and stir in the vegan sour cream until the sauce becomes silky and smooth. Mix well, and taste to adjust seasoning with additional salt or pepper if needed. The sauce should have a velvety consistency and a tangy, savory flavor.
Add the cooked pasta to the skillet and toss gently to coat the noodles evenly with the mushroom sauce. If the sauce feels too thick, stir in a splash of reserved pasta water to loosen it up and help it cling to the noodles. The pasta should be well coated and glossy.
Cook everything together for another minute, allowing the flavors to meld and the sauce to become perfectly velvety and warm. The pasta should be tender but not mushy, glistening with a rich coating of mushroom gravy.
Remove from heat, garnish with chopped herbs if desired, and serve immediately. The dish is ready to enjoy with its creamy, earthy, and smoky notes, feeling cozy and satisfying.
