Place each chicken breast between two pieces of plastic wrap and pound to an even thickness of about 1/2" with the flat side of a meat mallet or rolling pin.

Sprinkle each with your favorite seasoning mix, to taste, and lightly dust both sides with flour (optional). Press so seasoning adheres.

Place a heavy frying pan large enough to contain both chicken breasts over medium-high heat. Add the cooking oil and heat until it shimmers. Add the butter and let it melt briefly; add the chicken and cook, turning once, until the chicken is just done through, 4 - 5 minutes per side. Drain on paper towels; allow to rest 5 minutes before serving.