Put the onions in a large saucepan with the oil and gently fry for 5 minutes or until softened and golden brown. Add the garlic and cook gently for 1 minute.
Add the red peppers and half the courgettes and fry for 5–8 minutes or until softened and brown.
Add the stock or water to the pan with salt and pepper and bring to the boil. Reduce the heat, cover the pan and simmer gently for 20 minutes.
When the vegetables are tender, blend the mixture in batches, to a smooth soup and return to the pan. Season to taste, reheat and serve topped with the remaining chopped courgette and garnished with yogurt or a swirl of cream and chopped chives. This vibrant and warming soup is ideal for any meal and tastes just as good warm or cold.