Bring a large pot of salted water to a boil and cook pasta until just al dente. Reserve ¼ cup pasta water, then drain.

Heat 1 tablespoon oil in a large skillet over medium-high heat. Add half the mushrooms in an even layer and let them sit 2 to 3 minutes without stirring. Stir and keep cooking until browned. Transfer to a plate and repeat with remaining mushrooms and oil.

Lower heat to medium. Add onion to the skillet and cook 3 to 4 minutes until soft. Stir in garlic, paprika, and thyme and cook 30 seconds.

Sprinkle flour over the onion mixture and stir for 1 minute.

Slowly pour in broth while stirring. Add soy sauce, Dijon, salt, and pepper. Simmer 3 to 5 minutes, stirring often, until the sauce looks glossy and lightly thick.

Turn heat to low. Stir in vegan sour cream until smooth.

Add browned mushrooms back to the skillet. Toss in pasta and stir until coated. If sauce feels too thick, add a splash of reserved pasta water.

Taste and adjust salt, pepper, and Dijon. Serve hot with extra black pepper.