Peel and cut the potatoes into 1 inch-sized squares and boil until soft. Meanwhile thinly slice the red onion and fry in the margarine until soft, add two tbsp balsamic vinegar and allow the vinegar to evaporate. Set aside for a moment.

Drizzle the pan with olive oil and bring to a high temperature. Throw in the potatoes, sweet potatoes and rosemary, then fry until they start to take on a golden colour. Splash in the remainder of the balsamic vinegar. Add the onions, season and fry further until piping hot and golden brown.

Serve with freshly pouched eggs.