Makes about 1½ cups
1 cup distilled white vinegar
1 cup white sugar
A 4-ounce tin of Colman’s mustard powder
1 tablespoon kosher salt
3 large eggs
Combine the vinegar, sugar, mustard powder, salt, and eggs in a blender and blend until everything’s well combined, 10 seconds or so.
Pour an inch or so of water into a small saucepan and bring it to a boil over medium-high heat. Grab a heatproof bowl that’ll sit on the saucepan without touching the water, transfer the mustard mixture to that bowl, and set it on the saucepan. Cook, frequently stirring and scraping the sides with a rubber spatula, until the mixture thickens to a consistency that’s a bit looser than your average Dijon mustard, about 15 minutes.
Take the bowl off the pan, let the mustard cool, then cover and refrigerate until it’s fully chilled, an hour or so. It’ll thicken a bit more.
Use it now or keep it in an airtight container in the fridge for up to 3 weeks.