Bring a large pot of salted water to a boil. Cook the spaghetti until al dente, about 8–10 minutes. Save ½ cup of the hot pasta water before draining.

In a large skillet, heat the olive oil and butter over medium heat until the butter melts completely.

Add the minced garlic to the skillet and sauté for 1–2 minutes, stirring frequently until it becomes fragrant and lightly golden. Be careful not to let it burn!

Reduce the heat to low. Incorporate the grated Parmesan and shredded mozzarella into the skillet, stirring until the cheeses begin to melt.

Gradually add in the reserved pasta water, mixing until the sauce reaches a smooth, silky consistency. Adjust the amount of water to suit your preferred sauce thickness.

Toss the drained spaghetti in the skillet, ensuring the pasta is evenly coated with the cheesy sauce. Season with salt and pepper to taste.

Serve the pasta on plates and sprinkle with chopped parsley and extra Parmesan. Enjoy it hot!