Apple Puffed Pancake

My mom got this recipe from a bed and breakfast that she and my dad stayed at years ago. It is delicious!
2 medium baking apples (I like gala), peeled and sliced
4 T. butter

1 1/2 c. milk
6 eggs
1 c. flour
1/4 tsp salt
3 T. sugar
1 tsp. cinnamon
5 T. brown sugar

Preheat oven to 425, melt butter in a 9 x 13 baking dish in oven. Once butter has melted, add apples to dish and arrange in a uniform layer. Bake until sizzling. While apples are baking, whisk flour, salt, sugar, and cinnamon in a large bowl. Whisk eggs and milk in a separate bowl. Add wet ingredients to dry ingredients and mix well with a hand mixer on high. You want to the mixture to be frothy. Pour the mixture over your cooked apples and sprinkle with brown sugar. Bake for 20-25 minutes until puffed and golden brown.