1. Fill a pan with about 5cm of water. Add the vinegar and bring to a bare simmer.
2. Meanwhile, heat half a tablespoon of the oil in a large pan over a medium-high heat. Add the tomato slices, season with salt and pepper and cook for 1-2 minutes per side until just tender. Transfer to a plate.
3. Heat the remaining tablespoon of oil in the pan over a medium-high heat. Add the mushrooms and some salt and pepper. Cook, stirring occasionally, for 6-7 minutes until golden brown and soft.
4. Meanwhile, crack the eggs into separate ramekins or saucers. One at a time, slide each gently into the simmering water. Cook for 2-3 minutes for slightly runny yolks, or longer to your liking. Remove with a slotted spoon.
5. Top each slice of wholemeal toast with some sliced tomatoes and mushrooms, two eggs, a sprinkle of Parmesan and some salt and pepper. Serve immediately.