It's not necessary to cook lentils prior to adding them to your curry. Lentils absorb liquid. So when you add the lentils to your broth it will absorb most of the liquid creating a thick stew-like consistency that's perfect for putting on top of rice or quinoa, or sopping up with vegan whole wheat naan. If you prefer a thinner consistency I recommend preparing the lentils in a separate saucepan before adding them to the pot with the veggies, broth, and spices.