Line the tin with clingfilm, leaving enough to hang over the sides of a 20cm (8in) square, shallow cake tin. Break the biscuits into small pieces. Melt the two chocolates, syrup and butter in a heatproof bowl over a pan of simmering water, stirring occasionally. Make sure that the bottom of the bowl doesn’t touch the water. Mix together the biscuits, apricots, raisins, pecans and Rice Krispies. Stir these into the melted chocolate mixture. Spoon the mixture into the prepared tin and level the surface by pressing down with a potato masher. Leave to cool in the tin then place in the fridge to set (which will take 1–2 hours). To serve, turn out, carefully peel off the cling film and cut into 12 squares.