In a frying pan, heat the olive oil over medium-high heat. When hot, add the onions; cook, reducing the heat to medium, until slightly soft, about 3 minutes. Add the peppers. Continue to cook, stirring as needed, until the onions and peppers are very soft, about 15 minutes. Do not brown.
Preheat oven to 400° F.
Pour the onions, peppers and their cooking juices into a gratin dish. Add the drained beans and turn several times. Add a tablespoon or 2 of the reserved broth. Add salt and pepper to taste, plus the saffron, cumin and half the oregano, and the optional meat jus. Taste and adjust seasonings as desired.
To make the topping, cut the crust from the bread. Tear the bread into bite-sized pieces.
In a frying pan, heat the olive oil over medium high heat. When hot, add the bread and sauté until lightly golden, about 3 minutes. Sprinkle with a little salt.
With a slotted spoon place the fried bread bits on top of the beans and peppers.
Place in the oven and cook until bubbling and the bread is golden brown, about 15 minutes. Remove and sprinkle with the remaining oregano.