Add all the ingredients except cayenne pepper to a medium saucepan and simmer over low/medium heat for 5-7 minutes, or until it reaches the thickness you prefer.
Remove the sauepan from heat and add cayenne to taste. If more tang is desired, add a little more mustard. Use right away or store in an airtight container in the fridge.
Notes
* The powder can vary widely in terms of heat so I start with a small amount and add the powder in 1/4 teaspoon increments until it reaches the level of desired heat/ flavor.