Step 1

Heat the olive oil in a large heavy-based pan. Add the onions, carrots and thyme leaves, then gently fry for 15 mins.

Step 2

Stir in 1.4l chicken stock, bring to a boil, cover, then simmer for 10 mins.

Step 3

Add the leftover roast chicken, remove half the mixture, then purée with a stick blender. Tip back into the pan with the rest of the soup, the peas and seasoning, then simmer for 5 mins until hot through.

Step 4

Mix the Greek yogurt, garlic and lemon juice together. Ladle the soup into bowls, swirl in the garlic yogurt, then serve.

Step 5

If you want to use a slow cooker, gently fry the onions, carrots and thyme leaves for 15 mins, then tip them into the slow cooker with 1 litre stock. If you're using a chicken carcass, add it now. Cover and cook for 2-3 hours on High until the veg is tender. If you used a carcass, remove it now, shredding any remaining chicken from the bones. Stir back into the soup, or add the leftover roast chicken and frozen peas. Cook for 30 mins more. Remove half the mixture and purée with a stick blender, then serve as above.