In a bowl over a pan of simmering water, melt 300g dark chocolate and the vegetable oil.
In a seperate bowl, whisk together the eggs and the brown sugar until light and fluffy.
Add the melted oil and chocolate mixture to the egg mixture and whisk together until thickens.
Sieve in the plain flour, cocoa powder, salt and baking powder.
Cut the pitted cherries in half and stir through the brownie mix.
Place in a lined 7 inch square baking tray and bake for 32 minutes at 180°C fan.
Once baked, leave on the side to cool fully.
Meanwhile melt 150g dark chocolate in a saucepan with the custard. Once all combined together leave to cool.
Whisk the double cream with the vanilla extract until soft peaks.
Cut the remaining chocolate into shards.
Assemble by placing the chocolate custard in the bottom of the glass, followed by squares of cherry brownie, cherry pie filling, soft whipped vanilla cream and finally top with chocolate shards and a cherry.