Bring a large pot of salted water to a boil over high heat. Add spaghetti and cook until al dente, about 8–10 minutes. Reserve ½ cup of pasta water and drain spaghetti. Set aside.

In a large skillet over medium heat, cook the bacon strips for 5–7 minutes until crispy and golden brown. Transfer to a paper towel-lined plate to drain. Crumble into small pieces and set aside.

Drain excess bacon grease from the skillet, leaving about 1 tablespoon. Add sliced mushrooms and sauté over medium heat for 5–7 minutes until browned and tender.

Add minced garlic to the mushrooms and sauté for 1 minute until fragrant. Stir in pumpkin puree, dried thyme, smoked paprika, nutmeg, salt, and pepper. Mix well.

Pour in heavy cream and add grated Parmesan cheese. Stir continuously for 2–3 minutes until the sauce simmers and thickens.

Add cooked spaghetti to the skillet and gently toss to combine. If the sauce is too thick, stir in reserved pasta water gradually.

Serve spaghetti topped with crispy bacon pieces, fresh parsley, and additional Parmesan cheese if desired.