In a medium metal or glass mixing bowl, whisk together the mustard, turmeric and beer. Whisk in the beer, egg, cornstarch, salt, and vinegar.

Add 2 inches of water to a medium saucepan; bring to a simmer over medium-low heat. Set the bowl over the pan and cook, whisking constantly, until the mixture thickens – about 5 minutes.

Remove from heat and mix in the caraway seeds. Cool, then transfer to a jar and refrigerate.

The mustard will keep refrigerated for up to 2 weeks.