Begin by bringing a large pot of salted water to a rolling boil. Add 12 ounces of fettuccine and cook according to package instructions, usually around 10-12 minutes, until al dente. Reserve 1 cup of pasta water, then drain the pasta.

In a large saucepan over medium heat, melt 4 tablespoons of butter. Add 2 minced garlic cloves and sauté for about 1-2 minutes until fragrant. Pour in 1 cup of heavy cream and bring to a gentle simmer, thickening for around 3-5 minutes.

Reduce the heat to low and gradually whisk in 1 cup of freshly grated Parmesan cheese until melted. Season with salt and freshly cracked black pepper.

Add the drained fettuccine directly into the saucepan and toss to coat evenly. If the sauce is too thick, stir in some reserved pasta water.

For added heartiness, mix in 2 cups of cooked chicken and 1 cup of steamed broccoli if desired. Stir gently until well combined.

Remove from heat and transfer to serving plates, garnishing with freshly chopped parsley.