Julia Child's Beurre Blanc

White wine is reduced with white wine vinegar and shallots (and some chefs add cream for a stable, smooth sauce), then a whole lot of butter is whisked in slowly, piece by piece, and the mixture is seasoned with lemon juice. 

Use anywhere you'd like to drizzle a food with (or drown it in) better-tasting butter: on roasted or steamed vegetables, on shrimp or fish, on chicken, or, if you really are cheffy, on lobster or truffles.

Julia Child's Beurre Blanc (White Butter Sauce)

Makes 1 1/2 cups

• 3sticks cold unsalted butter (24 tablespoons), cut into tablespoon-sized chunks
• 1/4cup dry white wine
• 1/4cup white wine vinegar
• 1tablespoon minced shallots
• 1/4teaspoon kosher salt
• 1pinch white pepper
• 1/2teaspoon fresh lemon juice

1. Have the butter ready (cut and in a small bowl).
2. In a medium saucepan, bring wine and vinegar to a boil. Add shallots, salt, and pepper. Lower heat to a simmer and cook until most of the liquid has evaporated. (There should be about 1 1/2 tablespoons of liquid left. If you reduced it too far, add 1 tablespoon of water to remoisten.)
3. Remove pan from heat. Whisk 2 pieces of butter into the reduction.
4. Set pan over low heat and continue whisking butter into sauce a chunk at a time, allowing each piece to melt before adding more. Remember to maintain low heat and never let the sauce come to a boil once the butter is added, or the sauce will separate.
5. Remove sauce from heat and whisk in the lemon juice. Taste and adjust seasoning, then strain through a fine sieve into a bowl.
6. Serve with fish, poultry, or vegetables.

https://food52.com/recipes/39746-julia-child-s-beurre-blanc-white-butter-sauce