Wash the potatoes thoroughly and boil them in boiling water for about 20 minutes. Clean the leek, cut into rings and wash. Cut bacon into strips. Melt butter, fry leek and bacon for about 5 minutes. Mix eggs and double cream and milk. Season with salt and pepper
Cut the potatoes into slices and spread 1/3 of the slices on the bottom of a greased casserole dish. Spread half of the leek and bacon mixture on top. Place potatoes, leek and bacon again and finally potatoes in the baking dish.
Pour egg mixture over it. Grate cheese coarsely and sprinkle over the gratin. Bake in a preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: see manufacturer) for approx. 45 minutes until the gratin has set and is golden brown on top
Preparation time approx. 1 hour 20 minutes