Heat the oil in a pan. Fry the diced onions and ham over medium heat until the onions are translucent. Meanwhile, boil salted water with 40 g butter in a saucepan and cook the pasta until al dente. Preheat the oven to 200 ° C.
Mix the cream, creme fraîche and egg yolk in a bowl. Gradually add the beef stock, tomato paste, paprika powder, nutmeg, curry and water and season with salt and pepper. If you like, you can thicken the sauce with a little flour.
Cover the bottom of a greased baking dish with a little cream sauce. Layer alternately pasta and ham. Baste with the rest of the sauce. Then distribute the Tilsiter on it. If you like, you can also use more cheese. Bake the casserole in the preheated oven for 25-30 minutes.