First, cut ham, cheese, pickles and onion into small cubes and mix in a bowl.
Cut off the bun at both ends. Cut the ends into small cubes as well and add to the other ingredients in the bowl.
Hollow out the inside of the bun. Tear the hollowed out into small pieces and add to the other ingredients.
Add melted butter to the filling until it becomes a sticky mass.
Press the prepared filling into the hollowed out bun and put the Jägerwecken in the refrigerator overnight.