Cook the pasta following the directions on the packet.
Tip the contents of the sachet into a saucepan, add a splash of milk and mix well, then stir in remaining milk.
Bring to the boil, stirring continuously. Add the tuna, sweetcorn and cooked pasta, simmer for 1 minute stirring continuously.
Pour into an ovenproof dish. Top with crisps and cheese and place under a hot grill until golden. Enjoy with a mixed salad.