In a small saucepan, combine white wine, vinegar, and shallots. Bring to a simmer over medium heat and reduce until about 2 tablespoons of liquid remain.
Incorporate Butter
Lower heat to low and whisk in cold butter cubes gradually, one piece at a time, until fully incorporated and sauce is smooth.
Season and Serve
Season with salt and white pepper to taste. Keep warm until ready to serve.
Notes
Tip: Keep sauce warm on low heat; do not boil after adding butter or it will separate.
Variation: Add a splash of cream for extra richness.
Serving: Perfect over grilled fish, seafood, or vegetables.