Heat sandwich maker according to manufacturer's instructions. Place bottom half of English muffin on bottom plate of sandwich maker; top with cheddar cheese and turkey. Move top ring and egg cooking plate down. Pour egg onto cooking plate; sprinkle with a dash of kosher salt. Top with spinach and top half of English muffin. Close sandwich maker, and cook 5 minutes. Slide egg cooking plate out. Carefully place sandwich on a plate. Let stand 3 minutes.