Last Updated on April 6, 2025 by Jeroen Kaslanders
Combine 1 cup of tarragon, shallots, and peppercorns in a saucepan. Add white wine vinegar, white wine, and water. Set the heat to medium-high and bring the mixture to a simmer, stirring occasionally. Lower the heat to medium-low to keep a gentle simmer, allowing the liquid to reduce to approximately 3 tablespoons over 20 to 30 minutes. Once done, remove from heat. Strain the mixture into a bowl using a fine-mesh strainer, pressing the tarragon mixture to extract as much liquid as possible.
For the compound butter: In a mortar, combine 1/4 cup of chopped tarragon and capers. Use a pestle to mash them together for about 1 minute. Incorporate 1 tablespoon of cold butter, continuing to mash and pound with the pestle until the ingredients form a cohesive mass. Transfer the mixture onto a piece of plastic wrap, wrap it up, and refrigerate.
