Wash the cauliflower and remove the leaves. Carefully cut away the stalk without breaking the head. Bring a pot of salted water to a boil, add a dash of vinegar, then add the cauliflower. Cook for 20 minutes.
While the cauliflower cooks, prepare the mashed potato puree according to packet instructions, using the 500 ml milk. In a separate pot, cook the pasta in salted water according to packet instructions. Once done, mix the puree with the diced ham.
Place the cooked cauliflower on a platter. Arrange the pasta and ham puree around the cauliflower. Heat the bechamel sauce on medium heat until warm, then pour it over the cauliflower.
Insert a large knife or kitchen hatchet into the top of the cauliflower. Decorate the cut with ketchup or sprinkle red food coloring around it to create a dramatic blood effect for Halloween.