Preheat oven to 350°F (180°C). In bowl, stir together graham crumbs, coconut, walnuts, cocoa powder, sugar and salt. Stir in butter, egg and vanilla until combined; press into greased foil or parchment paper-lined 8-inch (2 L) metal cake pan. Bake until firm, about 10 minutes. Let cool in pan on rack.