1) Preheat oven to 325 degrees. Line cupcake pans with paper liners. Set aside.

2) In the bowl of an electric mixer fitted with the paddle attachment, combine flours, sugar, baking powder, and salt. Mix on low speed until combined. Add butter and peanut butter, mixing until just coated with flour.

3) In a large glass measuring cup, whisk together eggs, milk, and vanilla. With mixer on medium speed, add wet ingredients in 3 parts, scraping down sides of bowl before each addition. Beat 1-2 minutes, until ingredients are incorporated.

4) Fill the liners with batter, until about 1/2 full. Bake for 15-20 minutes, until the center of the cupcakes spring back when lightly touched and an inserted toothpick comes out clean.

5) Cool in pan for 10 minutes. Remove cupcakes and place on a cooling rack. Allow cupcakes to cool completely before frosting.

6) Combine butter, peanut butter, and salt with the paddle attachment. Beat until blended. Add powdered sugar and mix until well blended, 2-3 minutes. This will look dry and like a powder until liquid ingredients are added.

7) Add milk and vanilla and mix until smooth and creamy. The texture should be like ice cream.

8) Insert a cake decorating tip of choice into a pastry bag. Place the bag into a tall glass and fold the open end of the bag over the sides. Fill bag with frosting.

Pipe frosting onto cupcakes, beginning on the outside and working to the center.