Slice the chicken breasts into tiny, thin, bite-sized pieces. In a small bowl combine 2 TBSP soy sauce and sherry. Combine the chicken, soy sauce and sherry in a plastic bag and marinate for at least 2 hours. Drain and rise the miracle noodles. Cut them into 1-2 inch pieces. Heat in a skillet and cook until the water evaporates, stirring often. Continue to cook until the noodles reach your desired crispiness. Heat sesame oil in a pan. Add the onion, ginger and garlic and stir fry for 1 minute. Add the chicken and stir fry until fully cooked. Mix 4 TBSP soy sauce, rice vinegar and Sriracha in a small bowl. Drain the chicken and add it back to the pan with the noodles, mushrooms and soy/vinegar/Sriracha mixture. Cook until heated through. Serve with lettuce leaves.