Mix the lime juice, soy sauce and sugar and stir until the sugar has dissolved.
Dry-fry the sesame seeds in a nonstick frying pan over a medium heat. Shake the pan to move them around for 3–4 minutes or until the white seeds are lightly browned and popping. Spoon into a small bowl.
Bring some water to the boil in a saucepan. Reduce the heat to medium, add the mushrooms and cook for 4–5 minutes. Drain well, place in a bowl with the shallots, chillies and the sauce mixture and lightly mix together. Taste and adjust the seasoning.
Spoon over a pile of mixed salad leaves and sprinkle with the sesame seeds.