Season both sides of the steak well with steak seasoning and salt. Set aside until ready to cook.
Heat a saucepan on medium heat. Once hot, add half of the oil along with the shallots. Saute until browned. Then add the wine, broth, and half the rosemary. Simmer the sauce until it reduces by half or a little more than half depending on flavor (the wine should sweeten a bit). Taste and season with salt and pepper. Add in half of the butter and continue simmering until the butter is melted and the sauce has a slightly thickened consistency. Strain out the rosemary and shallot. Set aside. Rewarm if needed before serving.
Preheat a grill pan over medium heat. Very lightly grease one side of the peach slices with oil. Once the pan is very hot, place the peach slices greased side down into the pan until nicely marked then remove immediately and set aside. (if you do not have a grill pan do the same thing using a cast iron pan. If using a grill it is highly likely the peaches will stick and break apart without being very careful)
Heat a skillet or nonstick pan over medium heat. Once hot, add the remaining oil along with the steaks. Let the steaks get a nice crust on the bottom. Once the steaks have a nice crust flip them over and add the garlic cloves, remaining butter, and rosemary. Baste the steaks over top with the pan juices. Remove the garlic once soft and golden brown. Cook the steak to your desired temperature using a thermometer (see below). Let rest on a cutting board for 5 minutes before slicing against the grain. Lightly finish with kosher salt.
Serve the steak with grilled peaches and drizzle the sauce over top. Smear the garlic cloves onto the bread if desired.