1 1/4 cups all-purpose flour
1 1/2 tsp. baking powder
1/4 tsp. salt
3/4 cup sugar
6 Tbs. (3/4 stick) unsalted butter, at room temperature
1 whole egg plus 1 egg white, at room temperature
1 tsp. vanilla extract
1/2 cup milk
Preheat an oven to 350°F. Line a standard 12-cup muffin pan with paper or foil liners. (I baked at 325 for 20 mins )
In a bowl, whisk together the flour, baking powder and salt. In a large bowl, using an electric mixer, beat together the sugar and butter on medium-high speed until light and fluffy, 2 to 3 minutes. Reduce the speed to low and add the egg and egg white one at a time, beating well after each addition, then beat in the vanilla. Add the flour mixture in 3 additions, alternating with the milk in 2 additions, beating until just combined; scrape down the sides of the bowl as needed. Increase the speed to medium-high and beat just until no traces of flour remain, about 30 seconds; do not overbeat.
Divide the batter evenly among the prepared muffin cups, filling each about three-fourths full. Bake until the cupcakes are lightly golden on top and a toothpick inserted into the center of a cupcake comes out clean, 18 to 20 minutes. Transfer the pan to a wire rack and let cool for 5 minutes. Then transfer the cupcakes to the rack and let cool completely, about 1 hour.