Make the cakes according to the directions. Cool completely.
Wash the berries and dry thoroughly.
With the whisk attachment of a standing mixer, whip together the cream, vanilla, and sugar until soft peaks form.
Transfer half of the whipped cream to a large bowl. Carefully fold in half a pint of the blueberries and a half pint of the raspberries.
Spread the berry whipped cream evenly over the top of one cake.
Place the remaining cake on top of the smooth berry whipped cream. Cover the cake with the remaining plain whipped cream.
In the top left hand quarter, place 50 blueberries in a square (7 across and 7 down, plus one extra stuck in there) and the raspberries in 13 rows across (if you can fit them!). Add sparkling candles and enjoy!