Mustard sauce is perfect for meat sandwiches and goes well with both ketchup and mayonnaise. It's commonly used either as a dipping sauce or in stir-frying and goes well with bread dishes and fried foods, hamburgers, tacos, rice, barbecue, etc. The sauce can also be used as a topping for steamed or roasted veggies such as grilled or roasted sweet potatoes, steamed broccoli, and grilled zucchini.