Heat the oil in a large saucepan over moderate heat. Add the spring onions and garlic and cook for 2 minutes or until the spring onions are tender. Add the stock, the split peas, mint, marjoram, and a pinch of salt, and bring to the boil. Reduce to a simmer, cover and cook for 25 minutes.
Stir in the green peas and cook for a further 5 minutes or until both the split peas and the green peas are tender.
Transfer the mixture to a food processor and purée. Return the soup to the saucepan and gently cook for 3 minutes or until heated through. Swirl 1 teaspoon yogurt into each serving and top with a grinding of pepper.
Did you know?
Split peas are a good dietary choice for diabetics, as their complex carbohydrates (starches) are metabolised relatively slowly into glucose (sugar).