You take the stack of four cards and secretly hide them in your pocket before your performance. Your friend won’t notice the pack is missing these cards when they shuffle and split it. Taking the half of the shuffled pack they give you, just pretend to instantly memorise the cards - don’t worry, you really don’t need to remember them. Put the half pack in your pocket but make sure that the four hidden stack cards go on top of the pack and that you don’t disturb their CHaSeD order. Ask your friend to name any card. They could either mention.
