Cook the eggs in boiling water for 10 minutes, rinse and peel. Peel and finely chop the onion. Leave the diced ham in a pot. Add fat and melt. Sauté onions.
Sweat flour in it. Add mustard and stir in broth and milk. Simmer for 3 minutes. Season to taste with salt and pepper. Add eggs whole or halved to the sauce. Wash the chives, dab dry and cut into small rolls.
Put mustard party in a bowl. Sprinkle with chives and serve. Gherkins and mashed potatoes taste good with it.