In a heavy saucepan, melt the butter over medium heat. Add the garlic and sage and continue to cook until the butter brownish caramel color and has a wonderful, nutty aroma. Turn the heat to low and keep the butter warm. In a heavy bottomed pan, sear the Chateaubriand on all sides, before placing in a hot (400 degree) oven, use a spoon to liberally baste with the brown butter. Cook for thirty minutes, basting again every four to five minutes until done or an internal read thermometer reads 130 degrees. Remove from the oven and let rest ten to fifteen minutes. Slice and serve with a little of the brown butter on each plate.