Clean the fennel, cut eighths and cook for 8 minutes in boiling salted water. Then remove the stalk and cut the fennel into small pieces.
Prepare the tortellini according to the instructions on the packet.
In the meantime, cut the tomatoes and the cooked ham into small cubes.
Put half of the tortellini in a baking dish, place the tomatoes, the fennel and the boiled ham on top and cover with the remaining tortellini. Mix the sour cream with the milk and season with thyme, parsley, salt and pepper, then pour over the casserole and sprinkle with the cheese. Then put the whole thing in the oven at 180 ° C for 20 minutes.