Roast the fennel seeds and cumin seeds while stirring for 5 minutes. Take out of the pan.
Heat the oil and add the mustard seeds, black cumin seeds and sesame seeds. After a few seconds, reduce the heat and add the chilli, fennel seeds, cumin seeds, ground cumin and coriander, garam masala, fenugreek seeds, turmeric and cayenne pepper and cook for one minute while stirring. Add the potatoes and turn them in the spice mixture until they are covered all over.