for the whoopie pies
1/4 cup butter
1 cup sugar
2 tablespoons buttermilk
1 teaspoon vanilla extract
1 tablespoon red gel food coloring
1 1/3 cups all-purpose flour
4 tablespoons cocoa powder
1 teaspoon baking powder
1/4 teaspoon baking soda
1/2 teaspoon salt
for the coconut buttercream filling
1 cup (2 sticks) unsalted butter, room temperature
2 1/2 cups powdered sugar
1 can coconut milk, reduced to 1/3 cup (Reducing instructions below)
Seeds scraped from 1 split vanilla bean or 1 1/2 teaspoons vanilla extract
1/8 teaspoon salt
Preheat oven to 375F. Line a cookie sheet with silpat or parchment paper.
In a large mixing bowl, cream together butter and sugar. Add in eggs one at a time, beating after each addition. Beat in buttermilk, vanilla and red food coloring. In a separate bowl, whisk together flour, cocoa powder, baking powder, baking soda and salt. Stir the dry ingredients into the wet.
Scoop dough onto a lined cookie sheet using a generous small scoop (1 tablespoon or so). Bake at 375F for 8-9 minutes until centers appear set. Allow to cool slightly before removing wire cooling rack to cool completely.
To make the filling, first, make your reduced coconut milk: Bring coconut milk to boil in large deep saucepan over medium-high heat (coconut milk will boil up high in pan). Reduce heat to medium-low; boil until reduced to 1/2 cup (you will only need 1/3 cup for the recipe), stirring occasionally, 25 to 30 minutes. Remove from heat; cool completely. Transfer to small bowl. Cover and chill. Can be made 2 days ahead and kept chilled.
In the bowl of a stand mixer, beat butter until smooth. Add sugar, 1/3 cup reduced coconut milk, seeds from vanilla bean, and salt. Beat on medium-low speed until blended, scraping down sides of bowl. Increase to medium-high and beat until light and fluffy.
Pipe filling onto a cooled whoopie pie and sandwich on a second one. I refrigerate for a few hours, but let come back up to room temperature before serving.