Bring a large pot of salted water to a boil. Add spaghetti and cook according to package instructions until al dente. Drain and set aside.

In a skillet, melt 4 tablespoons of butter over medium heat. Add minced garlic and red pepper flakes, cooking until fragrant, about 1 minute.

Add the shrimp to the skillet. Season with salt and black pepper. Cook until shrimp are pink and opaque, about 3-4 minutes.

Stir in the remaining 2 tablespoons of butter and cooked pasta, tossing to combine. Remove from heat and stir in chopped parsley.

Serve immediately, garnished with additional parsley if desired.