Start by heating a large non-stick pan over medium-high heat. Add some oil or spray it lightly with oil.
Add the diced onion to the pan and sauté until lightly browned.
Stir in the diced mushrooms and cook until browned.
Add the cooked lentils and diced zucchini. Cook until the zucchini is tender.
Toss in the diced water chestnuts and cook for another minute.
Add the minced garlic and stir for one minute.
Season the mixture with salt and pour in the teriyaki sauce. Stir well.
Cook for an additional two minutes until everything is heated through.
Remove from heat and let cool slightly before serving.
Scoop the filling into the lettuce leaves and garnish as desired.
