Cook the Pasta:
Cook the pasta according to the package instructions. Drain and set aside.
Sauté the Onions and Garlic:
In a large skillet, melt the butter over medium heat. Add the chopped onion and sauté for 3-4 minutes until softened. Add the minced garlic and cook for another minute until fragrant.
Cook the Mushrooms:
Add the sliced mushrooms to the skillet and cook for 5-7 minutes, stirring occasionally, until the mushrooms release their moisture and become golden brown.
Make the Sauce:
Add the vegetable broth to the skillet and bring it to a simmer. Stir in the heavy cream, sour cream, and Dijon mustard. Season with salt and pepper to taste. Let the sauce simmer for 5-7 minutes until it thickens slightly.
Combine the Pasta and Sauce:
Add the cooked pasta to the skillet and toss to coat in the creamy mushroom sauce. If the sauce is too thick, add a splash more vegetable broth or cream to loosen it up.
Serve and Garnish:
Serve the creamy mushroom stroganoff hot, garnished with fresh parsley and a sprinkle of Parmesan cheese, if desired.