Add another ½ tbsp oil to the pan and fry the onion until softened and golden, about 10 mins. Tip in the tomato and cook for another 10 mins, or until collapsed, then add the garlic, chilli, cumin and ginger, and cook for 2 mins more. Return the aubergine to the pan, add the honey, the juice from the jar of preserved lemons and the dates. Season. Turn the heat down and simmer for about 10 mins, or until thick but not stiff – add a splash of water if you need to. Chop the preserved lemon – pulp as well as skin – discarding any seeds, then add half to the relish. Taste to see if you need more – it should be assertive, sweet and savoury. You may want more honey as well. Leave to cool, then stir in the mint.