Gremolata is a garnish made from chopped parsley, garlic, and lemon zest. It is traditionally served with rich osso buco, but here we have stirred it into beans for a refreshing accompaniment to Roasted Poussin.
Place beans in a large pan; cover with water by 2 inches; soak overnight. Drain beans; return to pan. Cover with water by 2 inches; bring to a boil. Reduce to a simmer; cook until beans are tender, adding water if necessary, about 1 hour. Drain and transfer to a bowl to cool.
Meanwhile, combine zest, garlic, parsley, and shallots in a bowl. Stir in olive oil, salt, and pepper. Stir gremolata mixture into cooled beans; let sit 1 hour for flavors to blend. Stir in tomatoes, and serve.