First boil the white peas or Kabuli Chana. They should be fully cooked.
Then cook or roast the sweet potatoes. You can roast them on oven or on stove top. Or else boil them in a pressure cooker.
Once they are boiled check the sweet potatoes with fork or knife. The fork should go through the sweet potatoes smoothly Then peel them.
Now take a mixing bowl and add boiled chick peas and pealed sweet potatoes. Then mash them in to a paste.
Now add salt, chili powder, garam masala, chopped onions, green chilis, garlic and coriander leaves.
Put sesame seeds as well. Now combine them . After that make equal size patties with the mixture.
Then heat the griddle or pan. Apply some oil on the griddle and place patties on top.
Grill them on the medium flame till they turn golden brown on both side. Serve them hot.