Char's dinosaur bbq potato salad

1. Cook the potatoes in boiling water to cover until tender. Without peeling, cut the potatoes into ¾-inch cubes and put them in a bowl. Snap off the tough bottoms of the stalks of asparagus and discard, then cook the tender tops in a shallow pan of simmering salted water until tender-crisp. Drain and shock in cold water. Slice the asparagus into 1 1/2-inch pieces and add to the potatoes. Cut the pepper into sticks about the same width and length as the asparagus. Put in the bowl. Add the red onion.
Mix up the dressing by stirring together the mustard, vinegar, brown sugar, salt, pepper, and garlic in a small bowl. Drizzle in the oil, whisking constantly to emulsify.
Add the dressing to the vegetables and give a good stir. Serve right away for best color in the asparagus.