Greek Aubergine and Courgette Soup

2 large aubergines, roughly diced
4 large courgettes, roughly diced
1 onion, roughly chopped
4 garlic cloves, roughly chopped
45ml / 3 tbsp olive oil
1.2 litres / 2 pints vegetable stock
15ml / 1 tbsp chopped fresh oregano
salt and ground black pepper
mint sprigs, to garnish

For the tzatziki:
1 cucumber
10ml / 2 tsp salt
2 garlic cloves, crushed
5ml / 1 tsp white wine vinegar
225g / 8 oz cup greek yogurt
small bunch of fresh mint leaves, chopped

Preheat the oven to 200ºC / 400ºF / Gas 6. Place the aubergines and courgettes in a roasting tin (pan). Add the onion and garlic, and drizzle over the olive oil. Roast for 35 minutes, turning once, until tender and slightly charred.

Place half the roasted vegetables in a food processor or blender. Add the stock and process until almost smooth. Pour into a large pan and add the remaining vegetables. Bring to the boil, season and stir in the chopped oregano.

For the tzatziki, peel, seed and dice the cucumber. Place the flesh in a colander and sprinkle with salt. Leave for 30 minutes. Mix the garlic with the vinegar and stir into the yogurt Pat the cucumber dry on kitchen paper and fold it into the yogurt. Season to taste and stir in the mint. Chill until required. Ladle the soup into bowls and garnish with mint sprigs. Hand round the bowl of tzatziki so that your guests can add a dollop or two to their soup.