Rinse the chicken livers and pat them dry
Trim away any fat, membranes, or green spots
Season with salt and pepper
Dredge lightly in flour if desired
Heat oil or butter in a skillet over medium heat
Add sliced onions or garlic if desired
Place the chicken livers in the skillet in a single layer
Cook for 2 to 4 minutes per side until browned
Reduce heat if needed to prevent burning
Cook until the livers are no longer pink inside
Remove from the pan and serve hot