Begin by bringing a large pot of salted water to a rolling boil. Add the spaghetti and cook according to package instructions until al dente, about 8–10 minutes. Drain and reserve ½ cup of the pasta water.

In a large skillet, over medium heat, add the chopped bacon slices. Sauté for about 5-7 minutes, until crispy. Remove bacon and drain on paper towels.

In the same skillet, add the unsalted butter to the bacon fat. Once melted, add the minced garlic and cook until fragrant, about 1 minute.

Pour in the heavy cream and bring to a gentle simmer. Gradually add the grated Parmesan cheese, stirring continuously until melted and smooth. Season with salt, pepper, and red pepper flakes if desired.

Add the cooked spaghetti and crispy bacon back into the skillet. Toss everything together until the sauce coats the pasta evenly. Add reserved pasta water as needed for consistency.

Remove from heat, transfer to serving plates, and garnish with chopped fresh parsley. Serve immediately.