Clean the kale, wash thoroughly and blanch in boiling salted water. Drain and cut coarsely. Dice bacon finely. Peel onions and cut into slices. Heat 30 g clarified butter.
Fry the bacon and onions in it. Add kale and braise. Add stock, bring to boil, cover and cook for 1 hour. In the meantime, wash the potatoes and cook in salted water for about 15 minutes.
Quench and peel the potatoes. Rinse lamb's leg slices briefly and dab dry. Heat the remaining clarified butter in a pan. Fry the meat for about 3 minutes on each side. Remove, season with salt and pepper and keep warm.
Add potatoes to the frying fat, season with salt and pepper, sprinkle with sugar and fry until golden brown. Season the kale again, arrange on plates with lamb's leg slices and potatoes.