For the sauce, in a small bowl, mix the ingredients together and set aside.
For the lentils, heat the oil in a frying pan over medium-high . When hot, add the onion, garlic and ginger and saute for about 5 minutes, until the onions softens and begins to brown.
Stir in the lentils and then the vegetable broth. Turn the heat to medium-low, cover, and simmer for about 10 minutes, until all the broth is absorbed and the lentils are cooked. Stir in the walnuts and about half of the sauce mixture, or to taste.
To serve, take a leaf of lettuce, fill it with the lentil-walnut mixture, top with carrot, green onions, and sesame seeds, and spoon as much sauce as desired over it all. Fold it like a taco and munch away!