Cook the pasta: Bring a large pot of salted water to a boil and cook your noodles according to package directions. Drain and set aside, reserving about half a cup of pasta water.

Sauté the aromatics: In a large skillet over medium heat, melt the butter. Add the diced onion and cook for about 5 minutes until softened and translucent. Toss in the minced garlic and cook for another minute until fragrant.

Brown the mushrooms: Add the sliced mushrooms to the pan and increase the heat to medium-high. Cook for 8-10 minutes, stirring occasionally, until the mushrooms release their moisture and start to brown. This step is crucial for developing deep flavor!

Create the roux: Sprinkle the flour over the mushroom mixture and stir well to coat everything evenly. Cook for about 2 minutes to remove the raw flour taste.

Build the sauce: Slowly pour in the vegetable broth while stirring constantly to prevent lumps. Add the soy sauce, Dijon mustard, and paprika. Bring the mixture to a gentle simmer and let it cook for 5 minutes until it thickens slightly.

Finish with cream: Remove the pan from heat and stir in the sour cream until fully incorporated. Season with salt and pepper to taste. If the sauce seems too thick, add some reserved pasta water to reach your desired consistency.

Combine and serve: Add the cooked noodles to the sauce and toss everything together. Garnish with fresh chopped parsley and serve immediately while hot.