Clean the mushrooms, wash if necessary and cut them into thin slices. Cut the ham into strips. Peel and finely chop the onion. Whisk eggs with salt and pepper. Wash chives, shake dry and cut into small rolls.
Briefly fry the onion, ham and mushrooms in hot butter. Pour eggs over it and let it simmer for about 2 minutes, stirring occasionally. Sprinkle with chives.