These are often served with a honey-mustard sauce. Whatever volume of sauce you decide to make, simply mix 2/3 yellow mustard to 1/3 honey. Whisk together until smooth and season with salt and pepper.
If you want to get fancy, try different mustards. Two good choices would be grainy mustard and dijon mustard. Grainy mustard has a deeper flavour as well as a tang from the addition of white wine. It also adds texture as the mustard seeds are whole, not ground. Dijon mustard also adds a deeper flavour and tang, but without the texture of the whole mustard seeds found in grainy. Both grainy and dijon mustards tend to have more of a "bite" than yellow mustard.