For the mustard, blitz together all the ingredients until smooth. Season with salt and pepper.
For the stick bread rolls, divide the dough into 4 pieces. Roll each into a long strip. Twist 1 strip around the end of a stick (about the thickness of your boerewors). Pinch the dough together to secure the end if necessary. Repeat with the rest.
Hold the stick over medium hot coals while rotating for about 5 minutes or until browned and cooked. Pull off the sticks.
Cook the boerewors on a grid at the same time over medium hot coals, turning occasionally, for about 10 minutes or until cooked.
Spoon the mustard into the stick bread holes and stuff with the boerewors. Serve with avocado seasoned with salt and pepper.
Tip: Buy 2 cm thick dowel sticks from timber shops.