Combine the caster sugar, chilli paste, juice of 1 lime and light soy sauce in a small mixing bowl and whisk until smooth.
Place the tofu in the marinade and let it sit for 15-20 minutes.
Meanwhile, blanch the baby sweetcorn then runner beans, in a large saucepan of salted, boiling water. Drain and refresh in a bowl of iced water.
Remove the tofu from the marinade and sprinkle over the flour, tossing well to coat evenly.
Heat the groundnut oil in a large frying pan and saute the tofu cubes all over until golden on the outside.
Combine the ginger, runner beans, baby sweetcorn and cucumber in a large mixing bowl and toss with the sesame seeds, remaining lime juice, red chilli and sesame oil. Add the tofu and toss well again.
Spoon into the open cabbage leaves and garnish with mint leaves and a wedge of lime before serving.