Remove the green peel from the zucchini with a peeler. Dice the zucchini.
Heat the butter or olive oil in a pan and sauté the chopped shallot and garlic in it. Add diced zucchini and stir-fry.
Deglaze with white wine. Add the mustard, salt and a small amount of water and simmer for 5-7 minutes until the zucchini is tender.
Put in a blender, add the grated lemon zest and purée finely until a silky sauce is formed. If necessary, bring to the desired consistency with a little more water and season with salt and freshly squeezed lemon juice.
For a bearnaise sauce, stir in the chopped tarragon.
Serve the sauce warm with freshly cooked asparagus.
Wellcuisine-Tipp
The hollandaise sauce gets the right consistency in my recipe with pureed zucchini. In order for the sauce to get the right color (and not turn green), the green peel of the zucchini should be removed with a vegetable peeler before use. The peel can then be used for the next salad.