Cook the fettuccine pasta according to package instructions in a large pot of salted boiling water until al dente. Drain and set aside, reserving 1/2 cup of pasta water.
In a large skillet, heat the olive oil over medium heat. Add the minced garlic and red pepper flakes (if using) and sauté for about 1 minute, or until fragrant.
Add the shrimp to the skillet and season with salt and pepper. Cook for 2-3 minutes on each side, or until the shrimp are pink and opaque. Remove the shrimp from the skillet and set aside.
In the same skillet, pour in the heavy cream and bring to a simmer. Stir in the grated Parmesan cheese until melted and smooth. If the sauce is too thick, add some reserved pasta water to reach your desired consistency.
Return the cooked shrimp to the skillet and toss to coat in the creamy sauce. Add the cooked fettuccine and mix until well combined.
Serve immediately, garnished with fresh parsley.