Heat oil in a large frying pan over medium high heat; brown sausages all over; remove and keep warm; drain oil.
Reheat frying pan over medium heat; add onion and apple, cook 2 minutes. Return sausages to pan; add combined MAGGI Favourites Devilled Sausages Recipe Base, water and tomato sauce; bring to the boil, stirring. Reduce heat and simmer, uncovered 10-15 minutes.
Meanwhile, place potatoes and garlic in a saucepan of boiling water and simmer until tender. Drain and mash well; add butter and milk, stirring well to combine. Serve sausages with mash.