"I'm a mustard fiend," says chef Bryan Voltaggio. At his DC-area restaurant Voltaggio Brothers Steak House, Bryan and his brother, Michael, serve every steak with a tray of sauces for dipping.

Chef Jeremy Nolen updates German classics at Brauhaus Schmitz in Philadelphia, including this intense mustard for sausages. In a medium bowl, combine the black and yellow mustard seeds with the ...