Halve the potatoes and cook them in a large saucepan of lightly salted boiling water for 10—15 minutes or until tender. Drain well.
Heat the oil in a wok or large, nonstick frying pan. Add the prawns, crushed garlic, finely sliced spring onions and cajun seasoning and stir-fry for 2—3 minutes or until the prawns are hot. Stir in the potatoes and cook for 1 minute. Transfer to a serving dish.
Peel, stone and dice the avocado and stir into the salad. Top with the alfalfa sprouts and serve.