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Thermidor Sauce
Serves 6 Prep 10 min Cook 30 min Total 40 min

Thermidor Sauce

This famous companion to lobster thermidor works with most crustaceans. It tastes wonderful mixed with crab meat and served au gratin.

Serves 6 Prep 10 minutes Cook 30 minutes Units Rate

Overview

A sophisticated, tangy cream sauce with mustard warmth and tarragon herbals. This classic accompaniment to lobster thermidor combines cheese sauce with white wine reduction and a distinctive mustard flavour profile.

Ingredients

Wine reduction base

  • 40 grams shallots (very finely chopped)
  • 200 ml Fish stock
  • 200 ml dry white wine

Sauce base

  • 300 ml Béchamel Sauce

Finishing

  • 100 ml double cream
  • 1 teaspoon Dijon mustard
  • 1 teaspoon English mustard powder
  • 50 grams butter (well chilled and diced)
  • 1 pinch cayenne pepper
  • 1 tablespoon tarragon (finely chopped)
  • salt

Method

Stage 1 - Reduce wine

  1. Combine the shallot, fish stock and white wine in a saucepan and let bubble until the liquid has reduced by two-thirds.

Stage 2 - Build sauce

  1. Add the béchamel and cook the sauce over a low heat for 20 minutes, stirring every 5 minutes.
  2. Pour in the cream, let bubble for 5 minutes, then add both mustards and cook for another 2 minutes.

Stage 3 - Finish

  1. Turn off the heat and whisk the butter into the sauce, a piece at a time. Season with salt and a good pinch of cayenne to taste.
  2. Finally add the tarragon, if using, and serve immediately.

Notes

  • Wine reduction: Reduce by two-thirds to concentrate flavours; this is essential to the sauce's character.
  • Mustards: Use both Dijon and English mustard powder for complexity; each adds different heat and flavour.
  • Cognac optional: Add a teaspoonful of Cognac at the end of cooking for extra richness, if desired.

Serving

Serve immediately with lobster thermidor, crab thermidor, and other crustaceans. Also excellent mixed with crab meat and served au gratin.

Storage

  • Best eaten immediately after preparation.
  • Keeps refrigerated for 1-2 days; reheat gently without boiling to prevent emulsion breaking.
  • Does not freeze well due to butter emulsion and béchamel base.

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