Boil the eggs for 10 minutes. Peel the onion and cut into very small cubes. Slice the cucumbers and eggs also cubes. Mix eggs, onion and cucumber with herbs (chopped), wine vinegar, mustard, the oil, sugar, salt and white pepper. Everything was passaged in a deep pot and put on fire. Add the butter and stir until sauce thickens. This sauce is suitable for grilled meat and vegetable salads. Can be served hot and cold.