Season the steaks with salt and pepper. Heat a little clarified butter in a pan. Fry the steaks in it over high heat, depending on the desired cooking level and thickness of the meat, for about 2-4 minutes on each side and then wrap in aluminum foil.
Divide the baguette crosswise into 4 sandwiches and halve each lengthways. Brush the top with mayonnaise and the bottom with the onion jam. Slice the steaks thinly and cover the sandwiches with them. Fold it up and enjoy.