In a large skillet, melt butter over medium heat.
Add chopped onion and cook for 4–5 minutes until soft and fragrant.
Stir in flour, parsley, pepper, garlic powder, and thyme until well combined.
Gradually whisk in chicken broth, stirring constantly to avoid lumps.
Bring to a boil and cook for 1–2 minutes until the gravy thickens.
Add sliced turkey one piece at a time, letting it heat through in the gravy.
Toast the bread lightly if desired.
Serve the warm turkey and gravy over bread slices to complete your Open-Faced Turkey Sandwich Recipe.