Shallot, lemon, and tarragon are classic pairings for many dishes. I like to infuse their flavors into a vinegar and then make a sauce to use over fish. The sauce is light and bright, adding many base layers of flavor to the fish.
Preheat a water bath to 135°F (57.2°C).
Lightly scrub the outside of the lemon then remove the zest with a vegetable peeler. Make sure little to no pith came off as well, using a paring knife to remove any. Combine the lemon peel, tarragon, shallot, and vinegar in a sous vide bag or mason jar then seal and place in the water bath. Heat the infusion for 1 to 2 hours.
Prepare an ice bath with 1/2 ice and 1/2 water. Remove the bag or mason jar from the water bath and place in the ice bath for 15 to 20 minutes. Strain the vinegar and store in a sealed container.
Whisk together the infused vinegar and honey. Slowly whisk in the olive oil until fully emulsified. Salt and pepper to taste. Serve over warm, white fish.
Because xanthan gum is a modernist ingredient, the amounts for this component are given in metric by weight. Learn more about how to measure modernist ingredients in this article.
I like to thicken this vinaigrette by blending in 0.15% xanthan gum. It also helps the vinaigrette cling to food when you use it.