In a medium saucepan heat oil over medium heat. Add onion; cook about 10 minutes or until tender, stirring occasionally. Add tomato puree, dried plums, brown sugar, the water, mustard, lemon juice, Worcestershire sauce, hot pepper sauce, allspice, and ginger. Bring to a boiling; reduce heat. Simmer gently, uncovered, for 5 to 10 minutes or until sauce thickens. Season to taste with salt and pepper.