Fill 1 litre water in a pot. Season with 1/2 tsp salt and 1/4 tsp of biryani masala or garam masala. Immerse the soya chunks in the boiling water. Allow to boil for 5-6 minutes. Drain in a sieve, pressing down with the bottom of a cup to remove all moisture from the rehydrated soya chunks.

Peel and roughly slice the sweet potato. In a small pan, take 1/2 cup water. Season with a pinch of salt and garam masala powder. Boil the sweet potato slices until a knife passes through easily.

Drain any leftover water, mash with a fork or round spatula and remove into a bowl.

In a mixer jar, blend the garlic, ginger, green chillies and fennel to a paste. Heat 1 tsp oil (or ghee) in a small pan. Saute this paste for 2-3 minutes on a medium flame. Add this to the sweet potato in the bowl. In the same pan, dry roast the oat flour until lightly fragrant.

In the same mixer jar, crush the soya chunks until coarsely mashed. Add to the bowl.

Combine with this the toasted oat flour, spice powders, adding around 1/2 tsp salt. Knead to get a smooth mixture. Check seasoning, and add a pinch more salt if you like.

Divide into 8 portions. Roll into balls, lightly flatten into patties. arrange in a dish, cover with cling film and refrigerate for 1 hour.

Coat a frying pan with oil. Once the oil is hot, shallow fry the patties on one side for 6-8 minutes.

Flip over and fry the other side also for 6-8 minutes until golden and crisp on the outside.

Serve with tamarind chutney.