Wash and cook the potatoes in salted water for 10 minutes. They should still be firm.
Drain and set aside.
Remove the yellow core of the kale and get rid the large green leaves on the outside. Wash the centre and chop very finely.
Peel and finely chop the onion.
Brown the lardons in the butter, then add the kale and onion, sauté for 2 or 3 minutes and then set aside.
Grill your steaks on both sides, preferably under a grill (for 2-3 minutes on each side), but depending how you would like them cooked, you can finish them off in an oven at 150°C.
Rest the meat for 5 minutes under some foil.
When you are ready to serve, brown the potatoes in the farmhouse butter and add the parsley. Season.
Remove the bones from the steaks and slice finely. Transfer to a serving dish and sprinkle with the fleur de sel.
You can serve the meat with Maître d’hôtel butter, which is actually softened butter with chopped parsley, salt, pepper, a dash of cognac and chopped shallot.
Serve with the kale and parsley potatoes.