In a large bowl, combine the pancake mix, milk, oil and egg. In an 8-in. ovenproof skillet, melt butter. Stir in brown sugar and apple slices; saute until sugar is dissolved. Pour batter over apple mixture.
Cook, uncovered, over medium heat until bubbles form on top of pancake. Bake, uncovered, at 350° for 12-17 minutes or until golden brown. Invert onto a serving platter. Serve with syrup. Yield: 1-2 servings.