Prepare the Chicken
Pat the boneless skinless chicken breasts dry with a paper towel to help the coating stick.
In a shallow bowl, mix the flour, salt, pepper, paprika, onion powder, and garlic powder.
Dredge each chicken piece in the seasoned flour, shaking off the excess but keeping a light coating.
Brown the Chicken
Heat olive oil or butter in a large skillet over medium-high heat.
When hot, add the chicken and cook for 4–5 minutes per side, until the coating turns golden brown.
Remove the chicken and set it aside on a plate.
Make the Onion Gravy
In the same skillet, melt the butter and add the thinly sliced onions. Cook until soft and golden, about 6–8 minutes.
Sprinkle in 2 tablespoons of the leftover seasoned flour and stir constantly for 1–2 minutes to make a roux.
Slowly pour in the chicken broth, whisking to remove any lumps, then stir in the milk or cream.
Smother the Chicken
Return the browned chicken to the skillet, nestling it into the gravy.
Reduce the heat to medium-low, cover, and let it simmer gently for 20 minutes.
The chicken will cook through while absorbing all that oniony, buttery flavor.
Serve
Let the chicken rest for a couple of minutes.
Serve with creamy mashed potatoes, white rice, or buttered egg noodles, and spoon that rich gravy right over the top.