Had this tonight and it was very good. Got it from a Grey Poupon ad in the latest issue (May '98) of Food & Wine magazine. The only change I made was I used 10 small red (new) potatoes instead of the six medium.

Mix first four ingredients in a small bowl. Put cut potatoes in a lightly oiled 13X9X2 baking pan or shallow baking sheet. Toss with mustard mixture. Bake at 425 for 35 or 40 minutes or until tender, stirring occasionally.