Heat oven to 220C/200C fan/gas 7. Cut the bread into bite-sized chunks and toss with the olive oil and some seasoning. Put onto a well-oiled baking tray and sprinkle on the grated Parmesan – try to get it on the bread as much as possible, rather than the tray, or it will stick. Cook for 10-12 mins until golden and crisp. Remove and cool.
Cook the potatoes in a large pan of boiling water for about 8 mins, then add the green beans and cook for about 2-3 mins more until both are tender. Drain and cool under cold running water, then set aside. Mix all the dressing ingredients with some seasoning and pour into the bottom of a large, deep container or bowl.
Layer up the salad on top of the dressing, starting with the potatoes, then the green beans, the salad leaves, the shaved Parmesan and finally the croutons. It is important to layer the salad in this order to stop the leaves wilting or the croutons going soggy. Chill until ready to go. To serve, toss all the ingredients together.