Put the chicken in a bowl with the soy sauce, 1½ tablespoons of the mirin, the oil and 1½ tablespoons of the caster sugar. Leave to marinate for 10 minutes.
Thread ¾ of the spring onions on to the skewers, alternating with the chicken and mushrooms, until used up.
Finely chop the remaining spring onions and add to a bowl with the mange tout and radishes. Add the remaining mirin and sugar, and squeeze the lime over the sesame seeds. Set aside.
Cook the skewers in a large frying pan or griddle pan over a medium heat for 15 minutes, turning often, until cooked through with no pink remaining.
Meanwhile, cook the rice to pack instructions. Serve with the chicken skewers and mange tout salad.