1Heat oven to 400°F. While oven is heating, melt butter in 9-inch glass pie plate in oven.
2Meanwhile, in small bowl, beat egg with wire whisk or egg beater. Beat in pancake mix, milk and vanilla. Pour over melted butter in pie plate. Arrange apple slices on batter. Sprinkle with cinnamon-sugar.
3Bake 15 to 20 minutes or until edges are deep golden brown. Serve warm with maple syrup.