In a pan set over medium heat, pour in the juices, zests, sugar and beaten eggs. Whisk all ingredients together until blended thoroughly.
Cook and constantly stir with a wooden spoon. Scrape down the sides frequently. The mixture should begin to coat the back of the spoon. Cook for about 8 to 10 minutes or until a candy thermometer reads 175 F. Cook and stir an additional 2 minutes, then add in the cubed butter.
Blend until the butter is melted and the mixture is smooth. If you wish, strain through a sieve to remove any small bits of egg white that may have formed.
Pour into jars and refrigerate. Use within 2 weeks.
Notes
Adapted from Stevie Parle, The Telegraph
Recipe by Just a Smidgen at https://justasmidgen.com/2013/03/29/dutch-babies/