Whisk eggs and milk in a deep plate. Spread 1 tsp. mustard on each slice of bread. Cover 4 slices of bread with 2 slices of ham and cheese each. Place the remaining slices of bread on top and press down gently.
Turn 2 sandwiches one after the other in the egg milk, let them drip off a little. Heat half of the butter in a pan. Fry 2 sandwiches on each side for 3-4 minutes on medium heat until golden brown and remove.
Clean the pan and melt the remaining butter in it. Turn the rest of the sandwiches in the egg milk and fry them in the same way. Serve with salted potato chips and - if you like it - strawberry jam.