For Brownie Bottom
5 ounces semi sweet chocolate, chopped
1/4 cup unsalted butter
1 large egg
1 large egg yolk
1/4 cup light brown sugar
1/4 cup all purpose flour
1/2 teaspoon vanilla extract
1/8 teaspoon salt
For Vanilla Cake Layer
1/2 cup unsalted butter, at room temperature (1 stick)
1 1/2 cups granulated sugar
1 cup all purpose flour
1/4 teaspoon baking powder
1/8 teaspoon salt
2 large eggs
3 1/2 tablespoons whole milk
1 teaspoon vanilla extract
Chocolate Glaze
8 ounces semi sweet chocokate
as needed white sprinkles