Drain chickpeas (discard liquid) and process in a food processor with broad beans, onion, garlic, spices, herbs and rind until a fine paste forms. Stir through flour and bicarbonate of soda, season to taste and roll into walnut-sized oval balls. Place on a tray lined with baking paper and refrigerate until chilled (15 minutes).
For lemon, cumin and chilli salt, dry-roast cumin seeds until fragrant (2-3 minutes). Pound with remaining ingredients in a mortar and pestle until coarsely ground, set aside.
Meanwhile, for yoghurt-tahini sauce, whisk tahini and lemon juice in a bowl until smooth, add yoghurt and garlic, season to taste and set aside.
Preheat oil in a deep-fryer or large deep-sided saucepan to 170C. Deep-fry falafel in batches, turning occasionally until golden and cooked through (3-5 minutes), remove with a slotted spoon, drain on absorbent paper and keep warm. Season to taste with lemon, cumin and chilli salt and serve with yoghurt-tahini sauce, pickled chillies, herb salad and flat-bread.
Note: You could use any delicate herbs for the salad; here we've used flat-leaf parsley, chives, mint and dill.