3 egg yolks
1 to 2 Tbsp (30 to 45 mL) homemade rhubarb vinegar or rhubarb juice
½ cup (125 mL) butter
Optional: 1 tsp (5 mL) finely crushed juniper berries
1 to 2 Tbsp (15 to 30 mL) boiling water (optional)
Melt butter in a small saucepan over medium heat until liquid and set aside. Whisk egg yolks in the top of a double boiler over barely simmering water until thick, about 3 minutes. (Make sure the water is not touching the bottom of the pan.) Stir in the vinegar or rhubarb juice.
Whisk in the melted butter in a slow stream in stages, about 2 tablespoons at a time, removing the double boiler from the heat periodically to allow the sauce to cool slightly. When all the butter is incorporated and sauce is thick, remove from heat. Stir in juniper berries.
If sauce becomes too thick to pour, whisk in one or two tablespoons boiling water—that is, if serving hot with cooked salmon or vegetables. As the sauce cools it will thicken, making it a perfect condiment for sandwiches or a delicious topping for salmon hors d’oeuvres.
Makes about ¾ cup (180 mL).
— Michele Genest, The Boreal Gourmet