kolrabi and bortolli bean gratin

2 kohlrabi, peeled and thinly sliced

2 large potatoes, peeled and thinly sliced

250g borlotti beans (before podding)

150ml double cream

150ml milk

150g hard cheese, grated into silvers 

freshly ground peeper

sea salt

pinch mace

• Preheat oven to gas mark 4.
• Pod the beans and boil in salted water for 10 minutes. 
• In an oblong casserole dish layer kohlrabi, potatoes, borlotti beans and cheese. Continue layers until just under the rim.
• Mix cream, milk, salt, pepper and mace in a jug.
• Pour the mix over the layered ingredients.
• Put into the oven for one hour.
• The gratin should be browned, cover with foil and return to the oven for another hour. 
• Lower the gas to mark 2, bake for a further 30 minutes or until the vegetables are soft.