Bring everything to the boil together and boil down (= reduce) until there are only 4 tbsp of liquid left. Pour through a sieve, cool down a little bit and then beat with 6 egg yolks until creamy, as for hollandaise. Stir in 125 g butter in flakes. Before serving, season again with salt, pepper, perhaps the juice of a lemon and/or meat extract.
The Bearnaise tastes exceptionally well with Châteaubriand and Entrecote. But it goes equally well with artichoke hearts, grilled salmon and other roast meat and fish dishes.