Put the fresh beans, if using, into a saucepan, pour in enough cold water to cover by about 5 cm (2 inches) and add the bay leaf, and garlic cloves. Bring to the boil and skim off any scum that rises to the surface. Reduce the heat to a simmer and cook, uncovered, for 25–30 minutes, or until tender. Drain, reserving the garlic cloves. If using presoaked dried beans, cook as for the fresh beans, but they will take about 1½ hours to become tender. The canned beans are ready to use.
Heat the oil in a large, heavy-based frying pan over a low heat. Add the onion, sage and crushed chillies and cook, stirring occasionally, for 10 minutes until the onion is softened. If you cooked the beans from scratch, squeeze the garlic flesh out of the skins into the pan. If using canned beans, simply add the chopped garlic to the pan. Cook, stirring, for 1 minute, then add the beans and the tomatoes. Season with salt and cook, stirring, for 3–5 minutes. Serve drizzled with a little extra virgin olive oil, if liked.