FOR THE CAKE:

1 cup (2 sticks) butter 

1 ½ cup mini marshmallows 

¼ cup unsweetened cocoa powder 

2 cups all-purpose flour 

1 teaspoon baking soda 

1 ½ cups sugar 

1 cup Dr Pepper 

½ cup buttermilk 

2 large eggs, slightly beaten 

2 teaspoons vanilla extract 

Preheat the oven to 350°. Grease a 13 × 9-inch baking pan.

In a medium saucepan over low heat, combine the butter and marshmallows. Cook over medium heat until the marshmallows are melted. Remove the pan from the heat, and stir in the cocoa powder. Set aside. 

In a large bowl combine the flour, baking soda, and sugar. Stir together using a large whisk. Add the Dr Pepper, buttermilk, eggs, and vanilla to the flour mixture, and stir until just combined. Slowly add the butter and marshmallow mixture. Stir until combined. 

Pour into the baking pan, and bake 30 to 35 minutes or until a toothpick inserted in the center comes out clean.

FOR THE ICING:

½ cup (1 stick) butter 

â…“ cup Dr Pepper 

3 tablespoons unsweetened cocoa powder 

1 tablespoon vanilla extract 

4 cups powdered sugar 

1 cup pecans, coarsely chopped 

While the cake bakes, combine the butter, Dr Pepper, and cocoa powder in a medium saucepan over medium-high heat; heat the mixture until it’s just boiling. Remove the pan from the heat, and slowly stir in the vanilla and powdered sugar. Spread over the warm cake. Sprinkle with the chopped pecans.

Serves 8 to 10