Take the meat out of the fridge at least 1 hour in advance, season with pepper and salt, and lightly rub with a bit of olive oil. Finely chop everything for the salad, season with pepper and salt, and mix in the lemon juice. Cut the baguette into 4 equal parts and slice them in half; spread some beurre café de Paris evenly on the top pieces and grill the 4 bottom pieces with cheese.
Preheat your grill. Place 2 slices of cheese on the grill and immediately place the bread on top, repeat 4 times. Let them melt nicely and turn golden brown. Place them on a board, distribute the salad on top. Grill the meat according to your desired doneness and slice it into very thin slices, remove the fat and distribute it over the salad.
Fry the fries until crispy and top generously. Put the lid on and press down a bit. Serve immediately. I really like to add some hot sauce for an extra kick, but you choose! Serve the rest of the straw potatoes alongside.