Peel and wash the potatoes and carrots and cut or slice them into thin slices. Clean, wash and cut leek into rings. Cut cabanossi into thin slices. Grease casserole dish.
Layer an outer ring of potato and cabanoshi slices in the form of scales. Then a ring of carrot slices and in the middle leek and rest of cabanoshi slices. Whisk cream and egg yolk, season with salt, cayenne pepper and Tabasco and pour over the top.
Sprinkle with pumpkin seeds. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for 35-40 minutes. Serve gratin garnished with parsley.