Line a shallow 20 cm (8 inch) square baking tin with clingfilm.
Heat 200g (7 oz) of the white chocolate in a heatproof bowl over a saucepan of simmering water, making sure the base of the bowl doesn't touch the water. Leave for a few minutes, stirring occasionally, until the chocolate is melted and smooth.
Remove the bowl from the pan and stir the Rice Krispies and apricots into the melted chocolate. Spoon the mixture into the prepared tin and press down firmly. Chop the remaining 50 g (2 oz) chocolate and scatter over the top. Place in the freezer for 15 minutes to chill and set.