Place mint leaves, coriander leaves, and green chilies (if using) in a blender. Grind to a very smooth paste. Add a little water if needed.

Transfer the paste to a deep bowl. Mix in lemon juice, ground cumin, sugar, and enough salt.

Now you can add in the yogurt. Start with ¼ cup of yogurt, and mix well. If you like the strong flavor of mint, use less yogurt. On the other hand, add more yogurt for a light flavor. (I added around 1 cup of yogurt as I prefer a very light flavor).