In a large nonstick skillet, heat about ¼ cup of the oil and fry the diced bread in batches until golden on all sides, about 20 minutes, adding more oil if needed. Drain on paper towels. Set aside.
In a large skillet, heat the remaining ½ cup oil and sauté the onions over medium heat for 5 minutes, or until soft. Add the fennel bulbs and sauté for 4 minutes more. Add the wine and simmer for 30 seconds. Add the water, fennel seeds and salt and pepper to taste. Reduce the heat to low and simmer for 10 minutes, or until the fennel is tender and most of the liquid has evaporated.
Reserve 2 tablespoons of the fennel fronds or dill for the garnish, add the remainder to the pan and cook for 2 minutes more. Taste and adjust the seasonings.
Place the fried bread on a serving platter, spoon the stewed fennel over it and sprinkle with the reserved 2 tablespoons fennel fronds or dill. Serve warm or at room temperature.