In a small frying pan, heat the oil over medium-high heat. Add the onion and sauté until translucent, 4 or 5 minutes. Add the garlic, bell pepper and ginger and sauté until tender, 4 or 5 more minutes. Sprinkle in the sugar, mustard powder, chile powder and pepper and cook, stirring frequently, until fragrant, a matter of a minute. Add the tomato paste, water, vinegar, Worcestershire sauce and soy sauce. Cook, stirring frequently, until the sauce comes to a boil. Lower the heat and simmer until the sauce has thickened a bit, about 3 minutes. Allow to cool. Refrigerate, covered, for up to 2 weeks.