Preheat the oven to 190°C, 180°C fan assisted, Gas mark 5.
In a pan, fry the mince until browned. Blend contents of the sachet with the water and add to the pan with the tomatoes. Bring to the boil whilst stirring, then simmer for 1 minute.
Empty the contents of the white sauce into a jug. Fill up to the 300ml mark with boiling water and stir until thick and smooth.
Beginning with the beef sauce, place alternate layers of beef and pasta into an ovenproof dish. Top with a layer of white sauce, sprinkle with the cheese and bake for 35-40 minutes until golden and bubbling.
Delicious with a mixed salad.