In a bowl mix the tamari and cornflour to make a smooth paste -if too thick add some water. Add mushrooms, spring onions, red pepper and garlic to the bowl and stir so that all the veg is covered with the paste.
In a wok or frying pan heat the olive oil. Add the vegetables and stir fry for 10-12 mins until golden brown. Set aside.
Fill the lettuce leaves with the veg mixture and drizzle over the sauce. Sprinkle over some sliced red onion and coraiander. Serve.