Remove skin from roast duck thigh and shred the meat. Set aside.
Blanch both shitake and button mushrooms for 1 minute. Drain and set aside. Blanch edamame beans in salted boiling water for 35 minutes. Drain in a colander. Combine mushrooms, shredded meat, edamame beans and avocado in a large mixing bowl.
Put dressing ingredients into a jug. Stir well to mix.
Pour dressing over the mushrooms and meat. Toss well to coat. Cover with a piece of cling film wrap and leave aside for 2025 minutes.
Remove core from lettuce then place the lettuce into a bowl of iced water. (This makes the lettuce easier to separate.)
Spoon mushrooms and meat mixture into lettuce cups. Sprinkle with a little toasted sesame seeds and serve immediately.