In a small, dry skillet, toast the pine nuts over medium-low heat, shaking the pan frequently, until fragrant and lightly toasted, about 2 minutes. Transfer to a small bowl.
Tear the toasted bread slices into bite-size pieces and put them in a food processor. Process until you have coarse crumbs, about 30 seconds. Transfer to a small bowl, drizzle with 3 Tbs. of the olive oil, mix well, and toss with 1 Tbs. of the chopped parsley.
Heat the oven to 375°F. In a 12-inch skillet (preferably ovenproof), heat 2 Tbs. of the olive oil over medium heat. Add the cauliflower and sauté until it begins to soften, about 5 minutes. Season with salt and pepper and continue sautéing until the cauliflower is deep golden brown and tender but still firm, another 7 to 10 minutes. Transfer the cauliflower to a small bowl.
Add the remaining 1 Tbs. olive oil to the skillet, still over medium heat. Add the onion and sauté until golden brown, 5 to 8 minutes. Add the saffron and stir to combine. Add the tomatoes and currants and simmer over medium-low heat until the sauce thickens and the currants plump, about 5 minutes. Remove from the heat and fold in the cauliflower, pine nuts, and remaining 1 Tbs. parsley. If the skillet isn’t ovenproof, transfer the mixture to a 9x9-inch shallow baking dish or a medium gratin dish.
Sprinkle the cauliflower with the breadcrumbs. Bake to heat through and meld flavors, 15 to 20 minutes. Serve hot.