Place the cabbage and noodles in a heatproof bowl. Cover with boiling water and stand for 4 minutes to soften; this will also turn your noodles purple. Fun!
Drain the noodles and place in a bowl. Place the cabbage sheets on a tray lined with paper towel to drain.
In a bowl, combine the chicken, spring onion, nuoc cham and fried shallots.
Working with one sheet at a time, soak the rice paper in a bowl of warm water for 10–20 seconds, or until just softened. Pop on a clean tea towel to absorb the excess water. Place a Thai basil leaf and then a cabbage leaf over the top. Add 2 tablespoons of the chicken mixture, then some noodles, cucumber and carrot.
First, roll up just the cabbage to create a small cabbage parcel, similar in size to what will be the rice paper roll. Then place it towards the bottom of the rice ¬paper sheet. Bring the bottom edge of rice paper up and over the cabbage roll, bring the sides in, then roll up to enclose the filling.
Place the roll on a serving plate and cover with a slightly damp cloth to stop it drying out. Repeat to make 12 rolls.
Cut in half and serve with lime wedges, extra nuoc cham and any remaining Thai basil leaves.