Bring a large pot of salted water to a rolling boil and add your pasta, stirring occasionally. Cook for 2 minutes less than the package directions to maintain a slightly al dente texture that finishes cooking in the sauce.

While water heats, warm olive oil in a large skillet over medium-high heat and sauté the sliced mushrooms for 4-5 minutes until golden. Season mushrooms with salt and pepper, then transfer to a plate and set aside.

Reduce heat to medium and melt butter in the same skillet, adding minced garlic and red pepper flakes for exactly 1-2 minutes until fragrant but not browned. This step prevents bitter garlic flavor that ruins delicate cozy quiet night meals.

Pour in heavy cream slowly while whisking constantly to prevent curdling, then add Italian seasoning and bring to a gentle simmer. The sauce for this cozy parmesan pasta weeknight recipe should bubble softly at the edges without boiling aggressively.

Remove from heat and immediately stir in grated Parmesan cheese in three additions, whisking between each addition until fully incorporated. Add lemon juice and adjust seasoning with additional salt and pepper to taste.

Drain pasta, reserving 1 cup of starchy cooking water, then add pasta to the cream sauce along with cooked mushrooms and fresh spinach. Toss gently for 2-3 minutes, adding reserved pasta water a splash at a time until the sauce reaches silky consistency.

Plate immediately and garnish with fresh chopped parsley and additional Parmesan cheese. Serve while steam still rises from each bowl.