Preheat oven to 350ºF. Prepare two 9" cake pans by greasing, flouring, and lining bottoms with parchment paper. This is a moist cake, do all three to make sure it doesn't stick.

In a large bowl, whisk together flour, sugar, baking powder, baking soda and salt. In a separate bowl, whisk the eggs, then whisk in the vegetable oil, buttermilk, and vanilla. Pour into flour mixture and gently fold together until no dry patches remain. Don't over-mix. Divide batter between prepared cake pans and bake about 35 minutes, rotating pans once. Cakes are done when the centres feel springy (not squishy) when gently pressed. If in doubt, pull out your thermometer - the internal temperature should be 200-205ºF. Let cakes cool 5 minutes in pans before transferring to wire racks to cool completely.

To make filling and topping:
Melt 6 oz of the white chocolate with ¼ cup of the cream in microwave on 50% power for 1 minute, until about 80% melted. Stir to finish melting (pop it in additional 10 second intervals on 50% power as needed). Allow chocolate to cool to room temperature.

Whip remaining cream to soft peaks in a stand mixer. Gently fold half of the cream into the cooled chocolate. Whisk sugar and vanilla extract into the rest of the cream in the stand mixer, then refrigerate it for topping later.

Place one of the cakes inside a 9" springform pan (or if your springform pan is larger, add a layer of parchment paper around the cake to make it snug). Top the cake with about ½ the can of pie filling, then the mousse, and finally the second cake. Refrigerate at least one hour, until mousse is set.

While cake chills, make the chocolate shards. Melt remaining chocolate in microwave for 1 minute on 50% power until 80% melted, stirring to finish melting. Spread in a thin layer over a 12" sheet of parchment paper, then carefully roll it up. Pop it in the fridge until hard.

Remove springform pan and top cake with reserved vanilla whipped cream and cherry pie filling. Unroll the chocolate and pile the shards on top.