1. Preheat oven to 300 degrees Fahrenheit.
2. Heat oil in a large, ovenproof pot over medium heat. Add pastrami and cook until lightly browned, about six to eight minutes.
3. Pour off all but two to three tablespoons remaining oil (if there is no extra oil it’s okay, too). Add onion and cook, stirring occasionally, until softened, about five minutes. Add one can of beans with its liquid.
4. Drain and rinse the remaining beans, then add them to the pot. Add molasses, ketchup, mustard, Worcestershire sauce, brown sugar, pepper, salt and about half a cup hot water. Stir well.
5. Bake for 30 minutes, stir, and bake for another 20 to 30 minutes. Stir one more time and bake for approximately 15 additional minutes, until beans are thick and deep golden brown. Add water to adjust consistency, if needed. Serve warm.