Heat 1 tablespoon of the vegetable oil in a large heavy-based frying pan and fry the minced beef for 10 minutes, breaking it up with a wooden spoon and stirring until browned and all the moisture has evaporated.
Push the meat to one side of the pan, add the remaining oil, fennel and celery and fry for 5 minutes until softened. Mix the cornflour with a little of the stock in a cup until smooth. Add to the pan with the remaining stock, tomato purée, potatoes and star anise.
Bring to a simmer, stirring, then reduce the heat and cover with a lid or foil. Cook gently for about 30 minutes until the potatoes are tender, stirring occasionally and adding a dash more water if the pan runs dry.
Stir in the soy sauce and sugar and cook for a further 5 minutes, uncovered if necessary to thicken the juices. Season to taste with salt and pepper and stir in the coriander before serving.