Preheat oven to 350 degrees.
Whisk together 4 cups of pancake mix and the granulated sugar.
In a separate bowl, mix together 3/4 cup milk, eggs, sour cream, and 2 tsp of vanilla.
Pour the wet ingredients into the dry ingredients and stir together. Spread evenly into a greased 9x13 baking pan.
In another bowl, add 1 cup pancake mix, brown sugar, cinnamon, nutmeg, salt, and 1/2 cup softened butter. Cut with a pastry cutter or fork until crumbly.
Sprinkle the brown sugar crumble topping over the pancake cake batter.
Bake in the oven at 350 for 40 minutes.
Make the icing by combining the powdered sugar, 1/3 cup melted butter, a splash or two of vanilla, and a few splashes of milk until desired consistency.
Pour the icing over the cake.
Allow to cool for at least 10 minutes. Serve and enjoy!