In a small bowl whisk together the eggs, sour cream and vanilla.
In a large mixing bowl mix together the flour, granulated sugar, brown sugar, cocoa powder, baking soda, baking powder, and salt.
Melt the butter with 1 cup of water (in the microwave or on the stove top). Using a mixer on low, add the butter mixture to the dry mix. When just combined, add in the sour cream mixture.
Pour the batter into a prepared* 18x13" baking sheet and bake in a 350°F oven for 15 to 20 minutes, or until a toothpick comes out clean.
While the cake is cooking, make the frosting by adding the butter, cocoa powder and milk to a saucepan. Bring the mixture to a gentle simmer, then remove from heat. Whisk in the powdered sugar until smooth. Stir in nuts, if desired.
Pour the warm frosting over the warm cake. Allow to cool completely before cutting.
Calories are automatically generated. For best results calculate based on your exact ingredients.*Prepare pan with butter and flour, or use a pre-made cake release. This is our recipe for the BEST cake release!