Cook the fettuccine according to package instructions.
While the pasta cooks, heat a large skillet over medium heat and melt the butter.
Add minced garlic to the skillet and sauté until fragrant, about 1 minute.
Season the chicken thighs with smoked paprika, onion powder, cayenne, salt, and pepper, then add to the skillet.
Cook the chicken for 6-7 minutes per side, or until golden brown and cooked through.
Remove the chicken from the skillet and let it rest for a few minutes before slicing.
Add heavy cream to the skillet, stirring to combine with the remaining flavorful bits.
Adjust the sauce's consistency with reserved pasta water if needed, then season to taste with salt and pepper.
Toss the cooked fettuccine in the sauce until well-coated.
Slice the rested chicken and place it on top of the pasta before serving, garnishing with fresh parsley.