*Percent Daily Values are based on a 2,000 calorie diet. Your daily values may be higher or lower depending on your calorie needs.
**Nutrient information is not available for all ingredients. Amount is based on available nutrient data.
(-)Information is not currently available for this nutrient. If you are following a medically restrictive diet, please consult your doctor or registered dietitian before preparing this recipe for personal consumption.
Bring onion, vinegar, oil, sugar, and Dijon mustard to a boil in a saucepan. Add mushrooms and simmer until liquid is slightly reduced, 5 to 6 minutes. Transfer mixture to a covered container and chill. Drain before serving.