Cupcakes
1 large egg
3 tablespoons sugar
3 tablespoons vegetable oil
1 teaspoon vanilla extract
1/2 cup/60 g all-purpose flour, sifted
1/2 teaspoon baking powder
pinch of salt
2 tablespoons milk
2 tablespoons confetti sprinkles, plus more for garnish

Cake batter frosting
1/2 cup/113 g unsalted butter, softened
1 cup/120 g confectioners' sugar
1 teaspoon vanilla extract
pinch of salt
2 1/2 tablespoons French Vanilla cake mix (I use Betty Crocker, of course!)
1 to 2 tablespoons milk, if needed