Sauce Piquante — Sharp Gherkin and Caper Espagnole

Ingredients

• For the reduction
• 2 tbsp shallots, finely minced
• 15 g unsalted butter
• 100 ml dry white wine
• 50 ml white wine vinegar
• For the sauce
• 400 ml demi-glace
• For the garnish
• 30 g cornichons, French, not American dill pickles; cut into 3 mm rounds
• 1 tbsp small capers, drained and rinsed
• 1 tbsp fresh tarragon, finely chopped
• 1 tbsp fresh chervil, finely chopped
• 1 tbsp flat-leaf parsley, finely chopped

Method

1. 1
   Melt the butter in a small saucepan over medium-low heat. Add the minced shallots and sweat, stirring occasionally, until fully translucent and without colour — they should yield no resistance when pressed against the pan.
2. 2
   Add the white wine and white wine vinegar. Raise the heat and reduce by two-thirds. This is where the dish lives or dies: the reduction must be intensely sharp, almost uncomfortable to taste alone — a polite, gently tart result means the sauce has already failed its purpose.
3. 3
   Pour in the demi-glace. Bring to a gentle simmer and cook for 15 minutes. The sauce should remain pourable — not a paste — and carry a deep savoury note beneath the acidity.
4. 4
   Pass the sauce through a fine chinois, pressing the shallots lightly. The liquid that falls through should be smooth and glossy, with no shallot fibre.
5. 5
   Return the strained sauce to the pan and bring back to a near-simmer. Add the cornichon rounds and capers to the hot sauce. The brine elements should be detectable immediately on tasting — sharp, saline bursts against the demi-glace body.
6. 6
   Remove the pan from the heat entirely. Add the chopped tarragon, chervil, and flat-leaf parsley. Stir once to distribute. The herbs must go in off heat — contact with hot liquid turns them grey within seconds. The finished sauce should be bright green-flecked and smell freshly herbaceous.