Put butter and brown sugar in microwave proof bowl, cook on High for 2 minutes. Stir until syrupy. Pour into a greased 9X13 baking dish. Slice french bread 1 1/2" thick. Place on top of syrup mixture in baking dish. Combine milk, eggs, vanilla in blender and pour over bread slices. Allow to soak overnight. Bake 45 minutes at 300.