You could, in theory, serve this sticky hoisin chicken tumbled over rice with the lettuce on the side, but where's the fun in that? It's a balancing act to ensure your leaf cup doesn't runneth over with the saucy, veg-packed mix before you get it to your mouth. It's a challenge you'll be happy to accept.
Using a box grater, coarsely grate carrot. Remove and discard woody stems from shiitake mushrooms and slice mushrooms. Thinly slice spring onions, keeping white and green parts separate. Crush garlic. Drain water chestnuts and roughly chop.
Trim chicken and cut into 1cm pieces.
Heat ½ the oil in a large frypan or wok over medium-high heat. Add chicken, season with salt and pepper, and cook for 2–3 minutes or until golden brown and almost cooked through. Remove from pan and set aside.
Heat remaining oil in the pan over medium-high heat. Add mushroom, carrot, white spring onion and water chestnuts with a pinch of salt and cook for 2–3 minutes or until softened. Add garlic and cook for a further 30 seconds or until fragrant.
Return chicken to pan with hoisin sauce, honey and sesame oil and cook for 1–2 minutes or until warmed through and sticky. Remove from heat and stir through most of the green spring onion (reserving a little to serve).
Cook rice according to packet instructions. Rinse and separate lettuce leaves. Serve chicken mixture in lettuce cups with rice and sprinkle with reserved green spring onion.