Creamy carrot soup

Make a comforting starter or lunch in no time with our easy, creamy, carrot soup, topped with garlicky seeded croutons. Quick and simple, it takes just 30 minutes to make

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1 1/2 tbsp oil 1 onion, sliced 1 celery stick, sliced 3 garlic cloves 2 crushed and 1 left whole 1 kg carrots, thinly sliced 1. 5 litre hot veg or chicken stock 1/2 small bunch of thyme 2 thick slices sourdough 1tbsp mixed seeds 1tbsp chopped parsley 1 1/2 tbsp double cream, plus extra to serve (optional)