Toast the bread in the preheated oven at 200°C for 5 minutes, until golden. Remove from the oven and rub a peeled garlic clove on each slice. Put the slices of bread in a large saucepan, cover them with the tomato purée and pour the vegetable stock on top until they are completely covered. Cook over a gentle heat for 30 minutes, add salt and pepper to taste and stir regularly.