1. Heat a broad non-stick pan, add the chana dal and dry roast on a medium flame for 6 to 7 minutes.
2. Cool slightly and blend it in a mixer to a fine powder and keep aside.
3. Heat the oil in the same non-stick pan. add the onions, ginger paste, garlic paste, green chillies and sauté on a medium flame for 3 minutes.
4. Add the yam, ½ cup of water, mix well and cover it with a lid and cook on a slow flame for 5 minutes, while stirring occasionally.
5. Transfer the mixture in a deep bowl and mash it well using a potato masher.
6. Add the prepared chana dal powder, mint leaves, chaat masala, garam masala, salt and mix well.
7. Divide the mixture into 6 equal portions and shape each portion into a flat round tikki.
8. Heat the oil in a deep non-stick pan, and deep-fry the tikkis on a medium flame till they turn golden brown in colour from all the sides. drain on an absorbent paper and keep aside. serve immediately with green chutney.
This recipe can make upto 6 tikkis.