Combine the lemon juice , shallot, salt and pepper . Leave it to sit for 5-10 minutes
Add the egg yolks and whisk with a hand blender
Melt the butter in a jug in the microwave . It needs to be hot with the hand blender going pour the butter in a steady stream . Add in most of the tarragon and blend , then fold through the rest . If it's too thick add a little water
Serve on top of your meat