This traditional Tuscan dish is very thick and filling. You should only use thick, good quality country-style bread. It's utterly yummy eaten hot with a generous grating of Parmesan cheese, but you can also serve it cold.
Pre-heat the oven to 150C. Spread the bread out on a baking sheet and dry in the oven for 10-15 minutes. Break into pieces.
Fry the onion in 2 tbsps of olive oil until just tender. Add the garlic and raise the heat slightly. As soon as the garlic begins to brown, add the tomatoes, salt and pepper. Simmer for 10 minutes. Cool slightly, then pass through the fine plate of a vegetable mill or liquidize and sieve.
Bring the stock to the boil and add the pureed tomato mixture, bread, remaining olive oil, basil, salt and pepper. Simmer for 20-30 minutes, stirring occasionally, until the soup is very thick. Taste and adjust seasonings. Serve hot or cold, with a drizzle of olive oil and, if you wish, a scattering of parmesan.