Chocolate cupcakes
- 1 box (15.25 oz) chocolate cake mix
- 1 cup buttermilk
- 3 large eggs + 1 egg yolk
- ½ cup vegetable oil
- 2 tablespoons sour cream
- 1 teaspoon vanilla extract
- 1 teaspoon espresso powder (optional, but enhances the chocolate flavor)
Marshmallow creme filling
- ½ cup (1 stick) unsalted butter, softened
- 1 jar (7 oz) marshmallow creme
- 1 cup powdered sugar
- 1 teaspoon vanilla extract
- Food coloring: green (Winnie), maroon/red (Mary), purple (Sarah)
Chocolate frosting
- 1 cup (2 sticks) salted butter, softened
- 3 ½ cups powdered sugar
- ½ cup unsweetened cocoa powder
- ½ teaspoon salt
- 2 teaspoons vanilla extract
- ¼ cup heavy cream (add more if needed)
Toppings