I've been looking a a whoopie pie cookbook and pan on Wililams Sonoma and Crate and Barrel for awhile. I finally caved and bought the book. My first experiment was chocolate whoopie pies with peanut butter filling.
Taken from Whoopie Pies by Sarah Billingsley and Amy Treadwell
Check out Bakerella for more information
Makes about 30 cakes (combine to make 15 finished whoopie pies)
Whoopie Pie Ingredients:
1 2/3 C all-purpose flour
2/3 C unsweetened cocoa powder
1 1/2 tsp baking soda
1/2 tsp salt
4 Tbsp unsalted butter, at room temperature
4 Tbsp vegetable shortening
1 C (packed) brown sugar
1 large egg
1 tsp vanilla extract
1 C milk
Peanut butter Filling Ingredients:
1 1/2 C creamy peanut butter
1 1/2 C (6 Tbsp) unsalted butter, at room temperature)
1 1/2 C powdered sugar
Directions for Whoopie Pies:
Position rack in the center of the oven and preheat to 375 degrees F. Line two baking sheets with parchment or Silpat mats.
Sift together flour, cocoa powder, baking soda, and salt. Using a stand or hand mixer, beat together butter, shortening, and brown sugar on low speed until just combined. Increase the speed to medium and beat until fluffy and smooth, about 3 minutes. Add the egg and vanilla and beat for another 2 minutes.
Add half of the flour mixture and half of the milk to the batter and beat on low until just incorporated. Scrape down the sides of the bowl. Add the remaining flour mixture and 1/2 C milk and beat until combined.
Using a spoon, drop about 1 Tbsp of the batter onto one of the prepared baking sheets and repeat, spacing about 2" apart. Bake one sheet at a time for about 10 minutes, or until the pies spring back when pressed gently.
Remove from the oven and let the cakes cool on the sheet for 5 minutes before transferring them to a rack to cool completely.
Directions for Filling:
Using a stand or hand mixer, beat together peanut butter and butter on low speed until smooth and creamy. Add the powdered sugar and beat on low to incorporate. Increase speed to medium and beat until the filling is light and fluffy, about 4 minutes.
Directions for Assembly:
Match up tops and bottoms based on size and shape. Spread filling on the flat side of one cak using a knife, spoon, or pastry bag. Top it with another cake, flat-side down.