Sauce Nantaise — White Wine, Shallot, and Butter for River Fish

Ingredients

• 2 shallots, finely chopped
• 200 ml Muscadet sur lie, dry, minerally, lees-aged Loire wine
• 250 g unsalted butter, cold, cut into 1 cm cubes
• 1 tsp unsalted butter, for sweating shallots
• to taste fine sea salt from Guérande
• 1 small bunch chives, whole batons, for service

Method

1. 1
   Melt the small quantity of unsalted butter in a heavy saucepan over low heat. Add the finely chopped shallots and sweat gently, without colour, until softened and translucent.
2. 2
   Pour in the Muscadet sur lie. Raise the heat to medium and reduce the liquid until only 2–3 tablespoons of concentrated wine essence remain in the pan. The reduction must be deep in aroma, carrying the mineral and yeasty character of the lees-aged wine.
3. 3
   Remove the pan from the heat. Begin whisking in the cold butter cubes one at a time, incorporating each fully before adding the next. This is where the dish lives or dies: the pan must be off direct heat throughout the butter mount — any overheating breaks the emulsion, and no vinegar is present to stabilise it as in beurre blanc. The finished sauce should be pale, glossy, and hold its body without visible separation.
4. 4
   Pass the sauce through a fine-mesh strainer, pressing lightly on the shallots. The result is a smooth, pale emulsion free of solids.
5. 5
   Season with Guérande fine sea salt. Taste for balance: the sauce should carry a clear note of Muscadet and shallot, with a butter richness that does not overwhelm. It should be noticeably paler and rounder than beurre blanc.
6. 6
   Lay a few whole chive batons across the surface of the sauce at the moment of service. The sauce is presented exclusively with fish — pike (brochet) is traditional.