step 1
In a saucepan, place the shallot, half the tarragon, the vinegar and 3 tablespoons of cold water.
step 2
Simmer gently until the liquid has reduced by half.
step 3
Place the egg yolks in a liquidiser and add the shallot mixture. Blend until smooth.
step 4
In a saucepan, melt the butter until it is bubbling.
step 5
With the liquidiser on, carefully pour in the hot butter a little at a time to form a thick, yellow sauceTaste and adjust seasoning. Add a squeeze of lemon juice and stir in the remaining tarragon. Pour into a warm sauce jug.
step 6
.