Alstertor Dusseldorf Style Mustard is a German mustard packaged in a distinctive beer mug. It is made with vinegar instead of verjuice, giving it a darker appearance and a more pronounced flavor compared to Dijon mustard. The heat level varies based on the mustard seeds used, which can include brown, white, or decorticated black seeds, resulting in a range from mild to very hot, offering versatility for various dishes.