Mini Funfetti Cake

Name: Mini Funfetti Cake
Prep time: 10 min
Cook time: 30 min
Total time: 40 min
Cuisine: American
Ingredients: 4 tablespoons unsalted butter, softened; 1/3 cup + 2 tablespoons granulated sugar; 1 teaspoon vanilla extract; 1 large egg white; 2/3 cup all-purpose flour; 1 teaspoon baking powder; 1/4 teaspoon salt; 1/3 cup + 1 tablespoon milk; 2 1/2 tablespoons sprinkles; 8 tablespoons (1 stick) unsalted butter, softened; 1 1/2 cups powdered sugar; 1-2 tablespoons milk (or cream); 1 tablespoon sprinkles