Spray a large non-stick frying pan with olive oil and set over medium heat. Cook garlic and ginger for 30 seconds, or until fragrant. Add chicken mince; cook, breaking up with a spoon, for 2 minutes, or until golden.
Add the diced mushrooms, brown rice, lentils, soy and oyster sauces, and cook for a further 1 minute, or until the mixture is heated through. Remove from heat. Stir through the sliced cucumber and shallots.
Serve the chicken mixture in whole lettuce leaves, topped with bean sprouts.