Remove any dirty and tough outer leaves from the sprouts, trim the bottoms slightly and then cut in half through the bases. Bring a large pan of lightly salted water to the boil and have a large bowl of iced water to hand. Blanch the sprouts for 2 minutes or until just tender when squeezed. Drain, then tip into the iced water. Chill for 15 minutes until completely cold, then drain again. This can be done the day before and then kept in the fridge until ready to use.