Chocolate and vanilla batters are swirled together in cupcake liners, baked, and then topped with strawberry buttercream. Sprinkles are not optional here!
Make the marble cupcakes: Line a standard size cupcake tin with cupcake liners.
Sift the flour, baking powder, and salt together in a medium bowl.
In a separate, larger bowl, cream the butter. Gradually add the sugar, and beat until light and fluffy. Add the egg and beat well.
In a small bowl, combine the milk and vanilla.
Add half the flour mixture to the butter and mix well. Add the milk and mix well. Add remaining flour and mix well.
Remove 3/4 cup batter and place into a small bowl. Stir in the melted chocolate.
Pour portions of both batters into the cupcake papers 2/3 full. Bake for 15 to 20 minutes, until the cakes spring back when touched.
Remove from oven and let cool for about 5 minutes, then turn the cupcakes out of the tins and onto a wire rack to finish cooling completely.
Make the frosting: Cream the butter in an electric mixer fitted with the whip attachment. Add the confectioners’ sugar and mix until just combined. Add the milk a little at a time. You may need more or less milk to reach piping consistency. Add the strawberry flavoring and mix until fluffy. Add pink food color a little at a time and beat until a bright pink hue is achieved. Scrape down the bowl and mix again as needed. Transfer the frosting to a piping bag fitted with a 1/2-inch open tip. Pipe frosting onto the cupcakes and top each cupcake with sprinkles.