In a large nonreactive skillet, melt 1/2 tablespoon of the butter in 1/2 tablespoon of the olive oil over moderately high heat. Lightly season the chicken with salt and pepper. When the butter stops foaming, add 2 pieces of chicken to the pan and sauté, turning once, until lightly browned and cooked through, 2 1/2 to 3 minutes. Transfer the chicken to a platter and keep warm in a low oven. Heat the remaining olive oil and another 1/2 tablespoon of the butter in the skillet and sauté the remaining chicken; keep warm. Pour off the fat from the pan.