Melt the butter in a casserole, make sure the butter is not boiling. Place the casserole on the side and let the butter rest a few minutes.
Chop the onion in small pieces.
Pour 2 tablespoons of water, the white wine vinegar, and the onion in a casserole, and let the liquid almost boil away.
Add the rest of the water in the casserole and lower the heat so the liquid doesn't boil again.
Add the egg yellows and stir until the sauce becomes thick and creamy.
Take away the casserole from the heat and place it on a wet towel.
While stirring add the melted butter slowly in the sauce, and continue stirring for 2 more minutes.
Continue to stir while adding the spices.
Serve immediately after so the sauce doesn't get cold and hard.