Preheat oven to 350°F. Prepare Mini Whoopie Pie Pan with vegetable pan spray.
In large bowl, sift together flour, cocoa, baking powder, baking soda and salt.
In large bowl, beat butter and sugar with electric mixer until light and fluffy. Add egg and vanilla extract; beat until well combined. Alternately add flour mixture and buttermilk in three additions, beating until just combined. Spoon one tablespoon batter into each pan cavity.
Bake 9-11 minutes or until tops of cakes spring back when touched. Cool in pan 3 minutes. Cool completely on cooling grid.
To assemble: Place cake in bottom of treat pop. Add a layer of cherries. Pipe a swirl of whipped icing from back edge following the curve of the container, then filling in the center. Continue layering until treat pop is full. Top with swirl of whipped icing and grated chocolate.