- In a small saucepan, add wine, onion, and parsley.
- Cook at a low simmer until wine reduces to nearly dry, “au sec.”
- Remove pan from heat, lower heat to lowest setting, and let sit about 30 seconds.
- Add butter to pan, a few cubes at a time, whisking until all butter is melted. Then add a few more cubes and repeat. Note: if butter is melting too slowly, return to the low heat for a few seconds, but not too long or the sauce will break.
- When all butter is incorporated, add a pinch of salt and white pepper to taste. Note: strain sauce through a fine strainer for presentation, then add more freshly chopped parsley.
- Place sauce in a spot on stove away from direct heat but keep warm until ready to serve. Always let the food you are adding it to cool a minute before saucing or the beurre blanc will break.