Preheat oven to 200˚Celsius/400˚F and place a wok and large skillet on the furnace. Keep an oven dish (preferably a high one) close at hand
Boil potatoes with some salt for 20- 25 minutes. Mash potatoes and stir with the hot milk, half of the grated cheese and the sellery. Add salt and pepper to taste.
Cook bacon in the wok crunchy and add the kale. Stir fry for about five minutes and then add the cream, stock and some salt and pepper. Let the kale simmer for ten minutes.
Cook the minced beef brown in the frying pan and break it up with a fork or spatula. Then add tomato puree and bring to taste with salt and pepper. Let this simmer on low heat for about five minutes. If you like spicy just add a few drops of tobasco sauce.
Put a layer of kale in the oven dish and put a layer of minced beef mixture on top. Repeat this in adding another layer of kale and beef on top. Finish off with a big layer of the potato mash and sprinkle the remaining grated cheese over the mash. Place in the centre of the oven for about 30 minutes. If you have a grill in the oven turn it ont in the last five minutes to give the cheese a crunchy golden crust.
Get the casserole from the oven, cut into four portions and distribute on plates. Enjoy!