Classic béarnaise sauce

Method

1. Put the white wine vinegar, peppercorns, shallot and blade mace in a small saucepan with 6 tbsp cold water. Heat gently until bubbling, then reduce until only 2 tbsp of liquid remain. Strain and allow to cool.
2. To make the béarnaise, put the reduction in a heatproof bowl set over a pan half-filled with gently simmering water (don’t let the bowl touch the water). Add the egg yolks to the bowl and whisk with a small whisk for 1-2 minutes. Have a small jug of iced water to hand. Turn the heat to low so the water bubbles very lightly, then add the first square of butter and whisk to dissolve. Once it has melted into the egg, add the second, and repeat in this way.
3. When you’ve added about half the butter, start adding the squares in pairs or threes. If the mixture starts to look at all greasy, or as if it might split, add a splash of iced water and stir. If the mixture doesn’t appear to be thickening properly (the finished sauce should thickly coat the back of a spoon), stop adding butter and whisk until it thickens, then continue to add the butter. Taste the sauce halfway through – if it needs more acidity, add a squeeze of lemon juice.
4. Once all the butter is incorporated, taste and adjust the seasoning and add a little water if the sauce is too thick. Press cling film lightly over the surface of the sauce. It will sit for up to 20 minutes (see tip) – stir from time to time. Just before serving, stir through the herbs to taste, along with 1-2 tbsp of the resting steak juices.