Place the lentils in a saucepan covered in water and cook until slightly tender. Sautée the onion over a medium heat until softened and add mushrooms, carrots, beans, and zucchini, cook for 5 mins. Turn down the heat and add the lentils, garlic, ginger, lemongrass, chilli and cook for an additional 5 mins. Add the chopped coriander and squeeze over the fresh lime juice. Serve in crispy lettuce leaf cups.