In a small saucepan, combine the white wine, white wine vinegar, and minced shallots. Bring the mixture to a boil over medium heat, then reduce the heat to low and simmer until the liquid is reduced by half.
Gradually add the cold butter, a few cubes at a time, constantly stirring until the butter is fully incorporated and the sauce is smooth and creamy. Be careful not to let the sauce boil, or it will break.
Season the sauce with salt and white pepper to taste.
Serve the beurre blanc sauce immediately, or keep it warm over a double boiler until ready to serve.
Notes
The sauce can be served with fish, shellfish, vegetables, or any other dish where you want to add a rich and creamy flavor. Enjoy!