Preparation of Cherry/ Cranberry filling: (Can be made a day ahead of time and refrigerated.)
Drain cherries reserving cherry juice. Combine sugar, cornstarch and (2/3 cup) cherry juice in a 2-quart saucepan.
Heat mixture until it comes to a full boil. Add cranberries. Let mixture simmer for 5 to 7 minutes until cranberries spilt open.
Add cherries and Kirsch and heat just until mixture returns to a boil. Pour mixture into a covered bowl and refrigerate until completely cooled.
Preparation of Cake:
Let butter and eggs come to room temperature (20-30 minutes). Preheat oven to 350°F
Prepare three round 9" x 1½" cake pans; lightly butter the sides and line bottoms with parchment paper.
Cream butter. Add sugar and cream together until light and fluffy. Add eggs one at a time, beating after each addition.
In a separate bowl, whisk together flour, cocoa, baking soda and salt. Add dry ingredients to butter mixture alternating with buttermilk.
Mix until well blended but do not over mix.
Divide batter evenly between 3 prepared pans. Bake 30 minutes or until top springs back when gently pressed and a wooden skewer inserted into the center comes out clean.
Cool 10 minutes, then remove from pans to a wire rack, peel off parchment paper and cool completely before assembling cake.
Preparation of the Whipped Cream filling: (prepare just before the cake is to be assembled.)
Combine gelatin and Kirsch in a small custard cup and let stand about 5 minutes to soften the gelatin.
Place the custard cup in a small pan of warm water and gently heat mixture over low heat, stirring until the gelatin has completely dissolved.
Remove from heat. Beat the cream in a chilled bowl until it holds soft peaks. Add powdered sugar and beat until it holds stiff peaks. Add in the gelatin mixture gradually beating until the mixture holds stiff peaks.
Preparation of Chocolate Icing: (Prepare after the rest of the cake is assembled and use immediately.)
Cream butter. Whisk together sugar and cocoa. Add sugar mixture alternating with Kirsch.
Beat mixture until fluffy adding only enough milk to make a thick spread-able icing.
Assembling the cake:
Place one layer, bottom side up, on a platter.
Spoon half the cherry/berry mixture onto the layer and allow the layer to absorb the syrup. Then cover with half the whipped cream mixture.
Place the second layer, also bottom side up, on top of the first layer. Cover with remaining cherry/ berry mixture (reserving about 5 cherries for garnishing the top of the cake.)
Top with the remaining whipped cream mixture.
Add third cake layer. Spread chocolate butter icing in the top of the third layer. Garnish with reserved cherries.