Preheat indoor or out door grill to high and oven to 375°F.
Heat a medium skillet over medium heat with 2 turns of the pan of EVOO, about 2 tablespoons. Add onions and season with some salt and pepper. Cook, stirring occasionally, for 7-8 minutes. Add the peppers, garlic, mustard, Worcestershire and hot sauce. Continue to cook until peppers are soft and onions are caramel in color, about 5 minutes.
Add the flour and cook for 1 minute, then add the beef stock and simmer until nice and thick.