Cut the crusts off the slice of bread and use a rolling pin to roll it flat.
Spread the entire piece of bread with peanut butter.
Spread with jam on top, but leave about 1 1/2 cm without jam on one end, just peanut butter (this helps it to stick shut).
Starting from the jam end, start rolling the bread tightly into a spiral towards the peanut butter end. Once rolled up, gently press shut so the peanut butter sticks.
Carefully cut into pieces about a cm thick.