Ingredients
for the cupcakes
2 ¼ c all-purpose flour
1 t baking powder
½ t kosher salt
1 ¼ c milk
4 large egg whites, room temperature
1 stick unsalted butter, room temperature
1 ½ c sugar
seeds from 1 vanilla bean or vanilla bean paste equivalent (if available)
2 t vanilla extract

for the frosting
1 c powdered sugar
1 c creamy peanut butter
5 T unsalted butter, room temperature
3/4 t vanilla extract
¼ t kosher salt
1/3 c heavy cream

Instructions

• Preheat oven to 350°F. Line cupcake pan with paper liners.
• In a large bowl, whisk together the flour, baking powder, and salt.  In a medium bowl, whisk together the milk and egg whites.  Set both aside.
• With an electric mixer, beat the butter, sugar, vanilla bean seeds, and vanilla extract at medium speed for 3 minutes or until the butter and sugar are very light.
• Add in one third of the flour mixture, beating at medium speed. Then alternating, add half of the milk/egg mixture, half of the remaining dry ingredients, the rest of the milk/eggs, and the remaining dry ingredients, being sure to fully incorporate the ingredients between each addition.
• Once ingredients are thoroughly incorporated, beat for 2 more minutes to ensure that it is thoroughly mixed and well aerated.
• Distribute the batter into 18 muffins, filling each 2/3 full.
• Bake for 18-24 minutes, or until a toothpick inserted into the centers come out clean. Cool on wire rack.
• Meanwhile, in the bowl of a mixer, combine the powdered sugar, peanut butter, butter, vanilla, and salt on medium-low speed.
• When well blended, add the heavy cream and continue mixing on high speed until the mixture is light and smooth.
• Frost cooled cupcakes in your favorite way (or just eat the frosting out of the bowl.  Just sayin’.)