Heat your oven to 220°C/Fan 200°C/Gas 7. Trim the top off the aubergine and slice the aubergine into small chunks. Pop in a roasting tin. Drain the chickpeas and rinse well. Shake dry and tip roughly 1/3 into the roasting tin (save the rest for a bit later). Sprinkle over a pinch of harissa (it’s spicy, so use a small pinch to start with unless you like things really hot) along with a little salt and pepper. Drizzle over 1 tbsp oil and toss together. Roast for 20 mins, till the aubergine is soft.
Meanwhile, peel and chop the onion. Peel and crush or finely chop the garlic cloves. Pour 1 tbsp oil into a large pan and bring to a medium heat. Slide in the chopped onion and garlic. Sprinkle in a pinch of harissa (remember, it’s spicy) and a little salt and pepper. Cook gently for 3-4 mins, till slightly softened.
Stir in the remaining chickpeas and crumble in the stock cube. Pour in 750ml boiling water. Return to the boil, then reduce to a simmer and cook for 15 mins. Grate the zest off the orange.
Slide the roast aubergine into the soup pan and squeeze in the orange juice. Use a stick blender to whiz into a smooth soup. No stick blender? Pour the soup into a blender (in batches if necessary) and blitz. Have a taste and add more salt and pepper if needed.
Ladle the soup into bowls and finish with the roast chickpeas and the orange zest.