Oooh, mustard sauce! I'll have to try this, although it is pretty sugary for my purposes.

My sister and I make mustard a lot, it is a sweet, hot mustard that is awesome with poultry and pork. It makes the nose run, the eyes tear and is SO awesome!

1 Cup of vinegar (I use apple cider, original recipe called for malt but I can't have that now since it contains gluten)
The equivalent of 1 cup of sugar (I use splenda but I'm sure you could find something more paleo)
2 oz of mustard flour (They sell Coleman's in 2 oz cans, or you can probably find it in bulk at a HFS)
3 eggs

Combine all the ingredients with whisk and cook in a double boiler, whisking, until it reaches 160' and starts to get thick.
Put in a container and store it in the fridge.