To prepare the chili sauce:

1. In a large cast-iron skillet over medium heat, combine the ground beef, onions, 1 tablespoon of the chili powder, mustard powder, salt, coriander, cumin, cayenne, bay leaf and garlic. Cook until the meat is browned and the onions are tender, about 8 minutes. Add the tomato paste and cook for another 2 minutes. Add the cider vinegar, then scrape any brown bits from the bottom of the skillet. Cook the mixture for an additional 2 minutes.
2. In a second skillet over medium heat, heat the oil then combine the remaining 2 tablespoons of chili powder and flour. Cook the chili-flour mixture for 2 minutes. Whisk in the chicken stock, and cook until thickened. Increase the heat to medium-high and simmer for 5 minutes.
3. Pour the chicken sauce over the meat mixture, and simmer 2 additional minutes. Discard the bay leaf, and salt and pepper, to taste.

To prepare the half-smokes:

1. Prepare an outdoor grill over high heat.
2. Butterfly each of the half-smokes lengthwise, and grill for 2 minutes per side.
3. Spread mustard on each of the bun halves. Place a half-smoke in a bun, and top with a generous serving of the chili sauce. Garnish with onions.