2 cups all-purpose flour
1 1/2 cups granulated sugar
1/2 cup light brown sugar, packed
3/4 cup unsweetened cocoa powder
2 teaspoons baking powder
1 1/2 teaspoons baking soda
3/4 teaspoon salt
3/4 cup oil, canola or vegetable
2 eggs
1 teaspoon vanilla extract
6 tablespoons milk
1/3 cup sour cream
1 cup boiling water
For the topping:
10.5-ounce package mini marshmallows
1/2 cup butter (1 stick)
6 tablespoons milk
3 heaping tablespoons unsweetened cocoa powder
1 teaspoon vanilla extract
3 cups powdered sugar
1. Preheat the oven to 350 degrees F. Grease a 9x13 baking pan.
2. Mix together the flour, sugars, cocoa powder, baking powder, baking soda, and salt in a large mixing bowl.
3. Add and mix oil, eggs, vanilla, milk, and sour cream until combined. Reduce the speed and pour boiling water in very carefully. Turn the mixer on high
for 1 minute to add air into the
batter.
4. Pour the batter into the baking pan then place in the oven. Bake for about 28 to 33 minutes or until a toothpick comes out clean.
5. Remove cake from the oven. Sprinkle marshmallows over the entire top of the cake.
6. Place it back in the oven for 2 to 3 minutes to melt the marshmallows.
7. Take it out of the oven. Allow the cake to completely cool before adding frosting.
8. While the cake is cooling, make the frosting. In a small saucepan, melt butter over medium-high heat.
9. Add milk and cocoa powder to the saucepan. Whisk. Cook for 2 to 3 minutes and stir constantly.
10. Take the pan off the heat and mix in vanilla and powdered sugar. Using an electric mixer, smooth the frosting.
11. When the cake is cooled, drizzle the warm frosting all over. Refrigerate for about 30 minutes before serving.