Remove the skin from the chicken fillets, pat them dry and cut them into thin strips. Drain the soaked mushrooms, discard the stems and slice the caps finely.
Heat two tablespoons oil in a wok. Add the garlic and chicken and stir-fry until chicken is cooked through and no longer pink. Add mushrooms, soy sauce, crushed Sichuan peppercorns and toss for two to three minutes.
Add salt, black pepper powder, half the spring onions and sesame oil. Mix and remove from heat and set aside. Heat plenty of oil in a wok. Deep-fry the noodles till crisp. Drain on absorbent paper. Crush the noodles and transfer into a bowl.
Add the chicken mixture and the remaining spring onions. Toss to mix well. Wash the lettuce leaves and pat dry and arrange them on a large platter. Just before serving take two lettuce leaves, spread the inside with hoisin sauce, place a spoonful of the filling, turn in the sides of the leaves and roll into a parcel. Similarly make more parcels. Serve immediately.