Peanut Butter Whoopie Pie
INGREDIENTS: 1 3/4 cups all-purpose flour 3/4 cup unsweetened cocoa powder (not Dutch process) 1 1/2 teaspoons baking soda 1/2 teaspoon fine salt 4 tablespoons unsalted butter, softened 1/4 cup vegetable shortening 1/2 cup granulated sugar 1/2 cup packed dark-brown...