||In a pot, add hot water and bring to boil. Add salt, onions and potatoes and boil until tender but not falling apart. Drain the potatoes and return to the same pot. Separate the onions from the potatoes and then add the garlic cloves and hot milk. Mash the potatoes with a potato masher until smooth. Set aside.
||In a heavy frying pan, add 1 tsp oil. Add the tenderloin and cook until a nice brown crust is formed. Flip and repeat for the other side. Add butter, and continue to cook, flipping steak occasionally and basting any light spots with foaming butter
||Rest the meat for at least 7 minutes. Serve by plating the mashed potatoes and steak at the center of a plate topped with a spoonful of the tapenade.