Method
Melt the butter in a pan.
In another pan bring some water to boil.
Place a metal bowl on top of the pan of boiling water.
Place the vinegar, lemon juice and egg yolk.
Whisk until frothy.
Gradually add the butter while continuing to whisk until all the butter is incorporated.
Ingredients
160g salted butter
1 egg yolk
25ml white wine or tarragon vinegar
A squeeze of lemon juice
