Coconut Whoopie Pies

Position oven rack in center of oven. Preheat oven to 375 degrees F. Line 2 baking sheets with parchment paper and set aside. Sift together the flour, baking powder, and salt onto a sheet of waxed paper. In a large mixing bowl, beat butter, shortening, and sugar until fluffy at medium speed of an electric mixer. Add egg and egg white, and beat until incorporated. Add half of flour mixture and half of coconut milk to creamed mixture; beat at medium speed just until blended. Add remaining half of flour and coconut milk and vanilla; beat until blended. Using a 1/4-cup ice cream scoop, drop batter into 12 mounds onto the prepared baking sheets, spacing them 2 inches apart. Or drop batter into 24 mounds by well-rounded tablespoons onto the prepared baking sheets. Sprinkle half of the mounds with coconut. Bake, one baking sheet at a time, until cakes begin to crack and are firm to the touch, 12 minutes for large cakes and 10 minutes for small cakes. Remove from oven and slide the parchment paper, with the cakes, onto a wire rack to cool completely. Use a thin metal spatula to lift the cookies off the parchment paper. Spread flat side of the plain cakes generously with Coconut Fluff Filling. Top with remaining coconut-topped cakes, pressing down lightly to seal them together. Coconut Fluff Filling: Beat butter and marshmallow cr?me in a large mixing bowl at medium-high speed of an electric mixer until fluffy, scraping sides of bowl as necessary. Beat in confectioners? sugar, coconut, coconut milk, and extracts until smooth. Makes about 1 3/4 cups.