Measure the cashew nuts into a small, heatproof bowl and cover with double the volume of hot water. Set aside.
Next, make the green dipping sauce. Toast the mustard and cumin seeds in a dry deep frying pan until the cumin smells fragrant and the mustard seeds start to pop. Remove from the heat and tip into a blender with the rest of the green dipping sauce ingredients. Blend until smooth (adding up to two tablespoons of cold water to loosen if you need – it should be like thick yoghurt), then taste and add more salt, lime or honey to balance. Cover and set aside.
Mix the onion, chilli powder, curry leaves, chilli, ginger, garlic, fennel and cumin seeds in a large mixing bowl and give it a really good scrunch. Season generously with salt and black pepper and leave to one side. Drain the cashews well and add to the bowl.
Add 3cm-depth of oil to the frying pan and heat gently over a low-medium heat. Add the bicarbonate of soda, chickpea flour and ghee to the mixing bowl along with 60ml of cold water and mix until it comes together in a chunky batter.
Test to see if the oil is ready by dropping a little of the mixture into the hot oil. If it sizzles and rises to the top it is ready. Add tablespoons of the mixture to the hot oil, a few at a time so as not to overcrowd the pan. Fry for a couple of minutes each side, using a slotted spoon to turn them over. Drain the cooked pakora on kitchen paper and continue until all the mixture has been used.
Season with a pinch of salt while warm and serve with the dipping sauce and some lime-dressed salad leaves if you like.