Bring the wine to the boil in a pan along with all the other ingredients up to and including the bay leaf. Turn down the heat, reduce the liquid to approx. 2 tbsp, strain into a thin-sided bowl, leave to cool.
Add the egg yolks to the reduction and mix well. Suspend the bowl over a gently simmering bain-marie, ensuring that the bowl does not touch the water. Beat the mixture with a whisk until light and fluffy. Reduce the heat, gradually add the butter while stirring, continue to stir until the sauce becomes creamy. Remove the bowl, season.
Mix the tarragon into the hollandaise sauce.