Wash the potatoes, wrap in aluminium foil and cook in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for approx. 1 hour. 10 minutes before the end of the cooking time, peel and finely dice the onion.
Whisk the eggs and season with salt and pepper. Cut the cucumbers into slices. Cut ham into cubes. Take potatoes out of the foil, cut them crosswise and open a little. Heat the fat in a pan and fry the onion.
Add whisked eggs and fry until scrambled. Add to the potatoes. Spread diced ham and cucumber slices on top. Wash parsley, dab dry and, except for something to garnish, chop finely and sprinkle on top.
Arrange on plates and serve garnished with parsley.