Add the ingredients for the tomato sauce to a food processor, and process until fairly smooth. Transfer the mixture to a frying pan, and bring to a simmer. Cook for at least 10 minutes, until the sauce has thickened and darkened slightly in colour. Season to taste.
Meanwhile, heat the oil in a large frying pan, and add the diced vegetables. Cook for 5-10 minutes over a medium heat, until fairly soft. Add the drained cannellini beans and sliced olives, along with the tomato sauce. Mix to combine, and season to taste.
Place the torn chunks of bread in a food processor, and process a few times so that some of the bread forms crumbs, with other pieces remaining chunky.
To make the herbed garlic butter, put the butter, minced garlic and chopped basil in a small bowl, and mix well (melt it in the microwave if you find it easier).
Heat the oven to 190°C (Gas Mark 5 / 375°F). Transfer the vegetable mixture to a large baking dish, and top with the bread. Dollop the garlic butter on top, and drizzle lightly with olive oil.
Bake for around 30 minutes, until the garlic bread crust is crispy and golden brown.