For the filling, beat the eggs, crème fraîche, salt and pepper with a whisk. Grate the cheese. Cut ham into cubes. Peel and finely dice onion. Stir ham, 200 g cheese and onion into the egg mixture. Cut the bread roll open.
Remove the inside of the roll (and discard or use for other purposes). Place the roll with the open side facing upwards on a baking tray lined with baking paper. Spread the filling into the halves of the buns. Sprinkle with remaining cheese and bake in a preheated oven (electric: 200 °C/ gas: level 3) for 15-20 minutes. In the meantime wash parsley, dab dry and chop finely. Serve the bread roll sprinkled with fried onions and parsley