Cover the base of a 5cm deep, 22x28cm (base) slab pan or tray with sponge finger biscuits, breaking if necessary. Drizzle with half the combined espresso and kahlua.
Carefully combine the mascarpone, caster sugar and cream together (don™t over mix or the mascarpone may split). Fold through the custard. Spoon half over the biscuits. Crumble over 2 flake bars. Top with half the mango and half the blueberries.
Using the remaining biscuit, coffee and custard mixture, repeat the layers. Cover and refrigerate overnight if time permits, at least 4 hours. Cover and refrigerate the mango and blueberries until serving.
Just before serving top with remaining mango, blueberries and flake chocolate. Serve.