Heat 1 tablespoon each butter and oil in large skillet. Add apple, working in batches if necessary, adding more oil and butter as needed; cook 4 minutes until light golden and speckled. Remove with spatula to large roasting pan or baking sheet with sides; spread in single layer; place in oven.
Heat another teaspoon butter and oil in skillet. Sprinkle pork with 1/4 teaspoon each salt and pepper. Add to skillet; cook 2 to 3 minutes per side until browned. Place each medallion on apple slice; there will be more apple slices than pork.
Add remaining butter and oil to skillet. Add onion, 2 tablespoons sage; cook 6 minutes until softened. Add cider and vinegar. Cook, stirring up browned bits, for 4 minutes until reduced and slightly thickened. Add remaining salt and pepper.
Arrange pork with apple slices on plates. Pour sauce over. Garnish each plate with a fresh sage leaf. Makes 4 servings.