Wostyntje, a Belgian ale brewed with mustard seeds, is on tap at Rich O's.
The Brouwerij de Regenboog ("rainbow" in Dutch) is located in a suburb of Brugge, Belgium, and as many times as I've visited, I've yet to make contact with the owner, brewer, bee keeper and chief bottle washer, Johan Brandt. He's been making plans to move the brewery elsewhere, perhaps all the way to Oudenaarde (in East Flanders), so perhaps I'll find him there someday.
Wostyntje is brewed with 90 % pilsner and 10 % munich malts, and Kent Goldings and Challenger hops. Dark candi sugar and crushed "Torhout Mustaard" seeds are added late in the boil, and light candi sugar is used to prime the bottled version. Alcohol content is 5% by volume.
The ale is a tawny golden or soft brown in color, and while there's not really a mustard flavor, a hint of spice and a mild bitterness seemingly not derived from hops serve notice of the not-so-secret ingredient's presence.
I'm dreaming of how Wostyntje complements food, and in particular, I'm imagining a pairing with the Waterzooi served at the Hotel Erasmus in Brugge.
Regenboog's 't Smisje Blond Ale (6% abv) also is on tap. The recipe is not at all complex: Pilsner malt, Challenger hops and spiced with lime (Linden) blossoms.