“I like to keep leftover cheese rinds in the fridge until I have enough to make a big batch of this broth (about half a pound). This salad also works well as a light soup: just add more broth until it’s a consistency you like. ”
Trim the celery, peel and trim the carrot, then cut, along with the radicchio, into 5mm cubes. Pick and finely chop the basil leaves.
Drain and rinse the beans and place in a bowl (save the remainder for another dish) with the radicchio, celery, carrot, onion and basil. Stir in the olive oil and vinegar, then season and leave to rest for 2 hours at room temperature.
Meanwhile, place the Parmesan rinds in a pot with 1.5 litres of cold water and cook slowly over a low–medium for 1 hour. Remove from the heat and leave the rinds in the water to cool.
Preheat the oven to 200ºC/400ºF/gas 6.
Cut the bread into 1cm cubes, scatter over a baking tray and toast in the oven until golden, about 20 minutes, tossing halfway through.
Divide the bean mixture between plates, then add a few tablespoons of the cooled parmesan broth. Garnish with croutons and the Parmesan rinds, finely sliced with a speed-peeler, if you like.