Cut the fillet into four thick slices and season it with salt and pepper to taste. Meanwhile, place the butter, garlic, and rosemary in a pan, then add the fillet slices and cook for a few minutes on both sides until they are golden brown. In the meantime, mix the ingredients of the croute with the butter and shape them as four medallions. Remove the fillets from the pan, put them on an oven dish, and place the crust medallions of Provolone Valpadana DOP over them. Bake them at 200° for about 5 minutes. Add the red wine, and when it is almost entirely reduced, add the demi-glace. Let it reduce to obtain a syrupy sauce. Now, remove the fillets from the oven, let them rest for about two minutes, then serve them with the sauce.