Beef pho

By Donal Skehan From Saturday Kitchen Ingredients For the broth 2 star anise 4 cloves 2 tbsp coriander seeds 1 large onion, unpeeled, halved 1 large thumb-sized piece fresh root ginger, unpeeled and halved 1.5 litres/2¾ pints beef stock 1 bone marrow, cleaned 3 …