Bring a medium pot of water to the boil. Add vinegar and bring back to a rapid simmer.

Crack eggs into the water. Simmer gently for 3 minutes (longer for well done). Remove eggs with a slotted spoon and pat dry on paper towel.

Meanwhile, divide yoghurt between two plates or shallow bowls.

When eggs are cooked, pop 2 eggs on each plate on top of the yoghurt. Drizzle with melted butter. Sprinkle with sumac (if using) and serve with salad leaves on the side.