Preheat oven to 375F.
Line a 9-in square baking pan with nonstick foil. .
In a microwave safe bowl, heat the chocolates and butter until fully melted.
Let cool a bit.
Add eggs and sugar until well combined.
Stir in all the dry ingredients and finally the root beer and vanilla.
Pour into your pan.
Bake for 28-30 minutes or until a toothpick comes out with only moist crumbs.