Drain the chickpeas and put in a large saucepan. Cover with cold water and bring to a boil, using a slotted spoon to skim off any foam. Reduce heat and simmer, uncovered, for 1-1 1/4 hours, or until tender, adding water if necessary.

Drain the chickpeas, reserving the cooking water. Season the chickpeas with salt and pepper. Put 2/3 in a food processor or blender with some of the cooking water and process until smooth, adding more cooking water as needed. Return to the saucepan.

Heat the oil in a medium saucepan, then add the onion and garlic and cook over medium heat, stirring frequently for 3-4 minutes, or until the onion has softened. Add the chard and rosemary sprigs and cook, stirring frequently, for 3-4 minutes. Add the tomatoes and remaining chickpeas and cook for another 5 minutes, or until the tomatoes have broken down to an almost smooth sauce. Remove the rosemary sprigs.

Add the chard and tomato mixture to the chickpea puree and simmer for 2-3 minutes. Taste and adjust seasoning if necessary.

Serve in warmed soup bowls with warm slices of toasted bread on the side.