First, slice your potatoes into fries and place them in a bowl of ice water.
Season your steaks with salt, pepper and garlic thoroughly, then set in the fridge to rest.
Preheat your grill to high heat (around 400F) for direct cooking.
Heat up a skillet with beef tallow until the fat is 350F. Dry off your fries and add them to the skillet. Cook for about 10 minutes per side on the fries or until they are golden brown and soft in the middle. Do the fries in 2-3 batches so as to not overcrowd the skillet. Once the fries are done, place them on a plate with a paper towel to catch the excess oil.
Add the fries to a bowl along with the parmesan, garlic, salt and chopped parsley. Toss until coated and keep warm until serving.
Drain the excess fat from your skillet then place it back over the flames. In a hot skillet, add your steaks to sear for 1 minute per side to develop a crust.
Add in the rosemary sprigs, crush garlic and beef tallow to simmer for 30 seconds. Push your steaks to one side of the skillet and place the herbs and garlic on top.
Begin basting the steak with the fat continually for 2 minutes then flip. Repeat this until your steaks have reached 120F internal. Once the steaks are done, pull them off and the steaks with the herbs and drizzle all the fat over top. Let rest until ready to slice.
Add the skillet back to the fire and deglaze with the sherry wine. Then add the rest of your Au Jus ingredients to the skillet to simmer for 8-10 minutes. Once done, pour your au jus through a fine strainer and keep warm.
Slice your bread in half and add some au jus to the inside. Slice your steak and top with more au jus and cheese. Melt the cheese and serve with the fries and au jus on the side. Enjoy!