Makes 1 cup
1/2 cup dry mustard powder
1/2 cup cider vinegar
2 egg yolks
1/2 cup maple syrup
COMBINE mustard powder with vinegar in a small bowl. Let sit for at least 2 hours or overnight.
BRING a small pot of water to a simmer. Scrape the mustard powder mixture into a large heatproof bowl. Whisk in egg yolks and maple syrup. Place the bowl over the pot of simmering water (creating a double boiler) and cook, stirring constantly until thickened, about 5 minutes.
SCRAPE into a small container and let cool fully. Refrigerate.