Peel the potatoes and cut into even-sized pieces. Bring to the boil in a pan of cold water and cook for about 15 minutes, until tender.
Meanwhile, heat the oil in a frying pan and cook the onions over a medium heat for 5-10 minutes, until soft, adding the garlic for the last minute.
Remove the skin from the sausages and shape the mixture into 20 balls. Add to the onion in the pan. Cook for about 5-10 minutes until the balls are golden brown and piping hot and no pink colour remains.
Stir in the tomatoes and beans, and cook for 5 minutes.
Drain the potatoes well and mash with the milk and sunflower spread.
Serve the mash with the sausage, tomatoes and beans.