Béarnaise

Béarnaise is hollandaise with a reduction. Simmer 60 ml white wine vinegar, 60 ml white wine, a minced shallot, crushed peppercorns and a few tarragon stalks until only about two tablespoons are left. Strain it. Use that in place of the water and lemon in a hollandaise: whisk it with three yolks over gentle heat, then beat in 200 g warm clarified butter off the heat. Finish with chopped fresh tarragon and chervil. It's the classic sauce for steak frites, and it's good with salmon too.