Prep your ingredients by dicing the chicken and chopping the garlic.

Cook the fettuccine in salted boiling water according to package instructions until al dente. Drain and set aside.

In a large skillet, melt 1.5 tablespoons of butter over medium heat. Add the diced chicken and season with salt and pepper. Cook until golden brown, about 6-8 minutes.

Stir in minced garlic and sauté until fragrant, about 1 minute. Add soy sauce, brown sugar, and red pepper flakes; mix well.

Toss in the cooked fettuccine along with remaining butter. Mix until well combined, adding reserved pasta water if needed for desired consistency.

Serve on plates, drizzling any leftover sauce over the top and garnishing with parsley if desired.