Peel and finely dice the shallot and crush the garlic clove. Place the shallots, garlic and thyme in a saucepan with the white wine and white wine vinegar. Bring to the boil and then reduce the liquid to about 30ml. Pass this through a fine sieve and keep the liquid.
Cut the butter into small cubes.
To make the sauce: Bring the liquid to the boil in a small sauce pan. Reduce the heat and start to whisk in the butter one cube at a time. Whisk continuously until all of the butter has been incorporated. Check the seasoning and add a squeeze of lemon juice.
«Fresh herbs such as tarragon and chives will make this a perfect accompaniment to a fish dish.»