Béarnaise sauce uses the same technique as hollandaise, but it is slightly thicker and has a much more concentrated and pronounced flavour because the flavourings are reduced. Serve with grilled or roasted lamb, beef and full-flavoured fish like salmon or monkfish.
For 300ml (½pint), boil 3tablespoons each white wine vinegar and dry white wine, 10 crushed peppercorns, 2–3 chopped shallots and 1tablespoon chopped fresh tarragon until reduced to 1-2 tablespoons. Strain, cool slightly and place in a heatproof bowl set over a pan of simmering water.
Whisk 2egg yolks into the reduction until foamy. Continue whisking over a low heat for about 3 minutes until the whisk leaves a trail on the surface. Remove from the heat and whisk in 125g (4oz) softened butter, a small piece at a time, until the sauce is thick. Stir in 1tablespoon chopped fresh tarragon.