- In large skillet cook mushrooms, pepper, and garlic in hot oil for 8 to 10 minutes or until most of the liquid has evaporated. Transfer to a bowl; stir in tomatoes, green onions, rice vinegar, cumin seed, and chili oil. Cover; chill in refrigerator at least 4 hours or up to 24 hours. Use a slotted spoon to serve relish. Makes 2-1/2 cups relish.