Grate the whole cheese. Clean, wash and possibly halve the spring onions. Peel, wash and cut the potatoes into large pieces. Put potatoes and spring onions in a greased casserole dish.
Preheat oven (electric cooker: 175°C/circulating air: 150°C/gas: level 2). Whisk cream, milk and eggs. Season with salt, pepper and nutmeg. Stir in cheese. Pour egg cream over the potatoes. Bake in a hot oven for about 1 1/2 hours.
Halve the bacon crosswise and after 20 minutes baking time spread it on the potatoes. Cover the casserole after 50 minutes if necessary. At the end of the baking time, prick the potatoes with a knife - if they are not yet soft, continue baking for 10-15 minutes.