Put the potatoes in a saucepan. Cover with boiling water, and cook for 15 minutes until tender.
Heat the vegetable oil in a frying pan. Add the sausagemeat and cook and stir for 3 minutes on medium heat until browned. Add the chopped onion to the frying pan, and cook for 5 minutes, stirring often. Add ketchup and chilli powder to the frying pan and cook for 3 minutes. Transfer the sausage mixture to an ovenproof dish then top with the baked beans.
Drain the potatoes and mash them with the milk. Then spread the mash over the baked beans and top with grated cheese.
Bake in the oven for 20 minutes until piping hot. Remove from the oven and serve.
If you do not have sausagemeat, you can chop up six sausages to use as a substitution.