Line a 20cm square baking tin with baking parchment.

Place the 200g of chocolate, butter and syrup in a heat-proof bowl and melt over a pan of barely simmering water or in the microwave. Once almost melted, remove from the heat and gently stir until any tiny bits chocolate have melted. Allow to cool a little.

Place the biscuits and 35g of the Maltesers in a freezer bag, seal and crush with a rolling pin. You want mainly crumbs but a few small chunks of biscuit is fine.

Top the crushed mixture and whole Maltesers (save 1 or 2 for yourself) to the melted chocolate and stir until everything is coated. Press into the prepared tin and make the topping.

For the topping, melt the chocolate, butter and syrup as before and spread over the biscuit base.

Cover the tin with cling film or foil and refrigerate for 1-2 hours before cutting into squares.