Mix together the semolina, chickpea flour, milled flaxseed, yogurt, onion, ginger, peas, chilli, salt, turmeric and most of the water. Allow to rest for 30 minutes.
Preheat the oven to 200°C. Oil a 23cm springform baking tin and line the base with parchment paper.Coarsely grate the courgette, squeeze out the excess liquid and add to the mix. Taste and adjust the seasoning if necessary.
Heat the oil in a small frying pan and add the mustard seeds and cumin seeds. Once the mustards seeds are popping, add the curry leaves, sesame seeds and sunflower or pumpkin seeds and cover the pan, as these will puff up and jump.
Once the sesame seeds are golden, take off the heat and add two-thirds of the contents of the frying pan to the batter. Adjust the water if necessary until the batter has a thick pouring consistency. Stir in the bicarbonate of soda.
Pour the batter into the prepared baking tin, cover with foil and bake in the oven for 20 minutes. Remove the foil and continue to bake for 10 minutes, or until the batter is cooked through and a cocktail stick (toothpick) comes out dry. Take out of the oven.
For a crispy top, brush and scatter over the remaining oil and seeds and place the cake on the upper oven shelf for a few minutes. It should be a lovely deep golden.
Cool a little before slicing and serve as it is, or with a chutney. If you are making this in advance, you can always toast the upper side in a frying pan until golden and crisp and scatter over the remaining seeds at that point.