For these a mixture of cooked vegetables is pressed onto the surface of each nan before cooking. 
Cooked vegetables such as potatoes, peas, and onions are ideal. Just mix with a little salt and garam masala and they are ready for use.
(Picture shows here are not original)
Here, thinly sliced onions are pressed into the nans before baking. 
For six kulchas, thinly slice two onions, sprinkle with salt, and leave to stand for about an hour. Drain off the liquid and pat dry with kitchen paper. Mix a teaspoon of garam masala and two teaspoons of finely chopped coriander with the onions and use by pressing onto the surface of each nan before cooking.
(Picture shows here are not original)