Step 1: Cook the pasta in a large pot of salted boiling water according to package directions until al dente. Drain and set aside.
Step 2: While pasta cooks, heat olive oil in a large skillet over medium-high heat. Add the sliced mushrooms and sauté for 6-8 minutes until golden brown and liquid has evaporated. Remove from pan and set aside.
Step 3: In the same skillet, reduce heat to medium. Add the diced onion and sauté for 3-4 minutes until translucent. Stir in the minced garlic and cook for another minute until fragrant.
Step 4: Whisk in the pumpkin puree, vegetable broth, Dijon mustard, and smoked paprika. Bring to a gentle simmer and cook for 5 minutes, allowing the sauce to thicken.
Step 5: Stir the cooked mushrooms back into the sauce. Remove the skillet from heat and stir in the sour cream until smooth and creamy. Season with salt and pepper.
Step 6: Toss the cooked pasta with the pumpkin and mushroom sauce. Serve immediately, garnished with freshly chopped parsley.