Preheat oven to 350ºF. Spray two 8" round cake pans with cooking spray.
In a large bowl, stir together flour, sugar, cocoa, baking powder, sod and salt. Make a well in the centre and add milk, oil, yogurt and vanilla. Stir until just combined.
In a large bowl beat egg whites until stiff peaks form. Fold 1/4 of egg whites to the chocolate mixture, then gently add remainder. Do not overmix. Divide evenly into pans. Bake 35-40 minutes. Do not overbake. Cool on wire racks.
ASSEMBLY: Filling: mix cherry pie filling with kirsch; set aside. Frosting: Whip cream until stiff peaks form. Add sugar and vanilla and beat one last minute. Remove 3/4 cup and set aside. Whip cocoa into remaining cream. Topping: Shave chocolate; set aside.
Slice each cake layer in half. Place the first layer on a plate and spread 1/2 of the cherry mixture on top. Add a cake layer, spread the vanilla whipped cream over this layer. Top with another cake layer, cherry mixture and final cake layer. Frost with chocolate whipped cream and top with chocolate shavings.
FILLING and FROSTING 2 x 540mL cans cherry pie filling 4 tsp kirsch or cherry brandy 2-1/2 cups whipping cream 1 Tbsp vanilla 1/4 cup sugar 2 Tbsp unsweetened cocoa 2 squares semisweet chocolate