In a large pot, bring salted water to a rolling boil. Add the fettuccine and cook according to package instructions until al dente, typically 8-10 minutes. Before draining, reserve 1/2 cup of the pasta water. Drain and set the pasta aside.
Heat a large skillet over medium heat. Add the olive oil and once warm, sauté the minced garlic until fragrant and golden, approximately 1 minute. Be careful not to burn the garlic.
Lower the heat to medium-low. Add the softened cream cheese to the skillet, stirring constantly until it melts and becomes creamy and smooth. Gradually mix in the sour cream, followed by the grated mozzarella and Parmesan cheese, stirring until the cheese melts and the mixture is well combined.
Gently stir in the thawed and drained spinach and the chopped artichoke hearts. If desired, mix in the red pepper flakes for an extra kick. Season with salt and freshly ground black pepper to taste. Allow the mixture to simmer for about 5 minutes, stirring occasionally, until it is heated through.
Add the cooked fettuccine to the skillet, tossing the pasta with the cheese sauce until coated evenly. If the sauce is too thick, slowly incorporate some of the reserved pasta water until you achieve your desired creaminess.
Once everything is well-mixed and heated through, remove the skillet from the heat.
Transfer the pasta to serving bowls and garnish with a sprinkle of freshly chopped parsley, adding a pop of color and freshness to the dish.
Notes
Adjust the red pepper flakes according to your heat preference.