Preheat oven to 350°F.
Grease 8x8 inch baking pan.
Prepare apple slices and set aside.
Combine dry ingredients in a large bowl.
Cut in butter until crumbly.
Make well in center.
In another bowl, beat egg until frothy.
Mix in milk and vanilla.
Pour into well and stir until just moistened.
Gently stir in apple slices.
Pour into greased pan and spread to the edges.
Mix brown sugar and cinnamon and sprinkle over top.
Bake at 350°F for 45-50 minutes or until center is set.
Serve warm with ice cream.