Preheat oven to 350 degrees. Grease a 13x9 inch glass baking pan.
1. Using a large bowl , stir the cookie mix with 1 Tablespoon flour. Place 1/2 cup softened butter and 1 egg in the bowl. With a fork, work the butter into the cookie mix until well incorporated and you have large clumps of dough.
2. Press the dough into the bottom of your prepared pan evenly. Bake 15 - 20 minutes or until the dough is set and lightly browned around the edges. Remove from the oven and set aside to cool.
3. While the dough cools, place 3/4 cup butter in a small saucepan, cook the butter stirring constantly until it becomes a golden brown color. Take the butter off the heat as soon as it reaches a golden brown color, place it in a measuring up to cool slightly.
4. Peel. core and thinly slice apples, layer them onto of the cooled cookie crust.
5. In a large bowl place the remaining topping ingredients (3 eggs, 3/4 cup sugar,1/3 cup flour , plus 1 Tablespoon flour, 1/2 Teaspoon salt and 1/1/2 Teaspoons vanilla). Beat until well incorporated. Using the mixer, gradually add the browned butter, beat until smooth. Pour mixture over the apples evenly in pan.
Bake 40 - 45 minutes or until deep golden brown and a tooth pick inserted in the center comes out clean. Cool completely on wire rack. Cut into squares, serve.