Preheat oven to 350°F. For the Cake, grease 2 (9-inch) round cake pans with oil. Set aside. Mix cocoa powder, cornstarch, sorghum flour, tapioca flour, xanthan gum, baking powder, baking soda and salt in medium bowl. Set aside.
Reserve 1/4 cup of the coconut milk for the Frosting. Beat granulated sugar and oil in large bowl with electric mixer on medium speed until well blended. Add melted chocolate; mix well. Beat in eggs, 1 at a time. Stir vanilla into coconut milk. Gradually beat in flour mixture alternately with coconut milk mixture on low speed until just blended. Do not overbeat. Pour batter into prepared pans.
Bake 40 to 45 minutes or until toothpick inserted in center comes out clean. Cool in pans 10 minutes. Remove from pans; cool completely on wire rack.
For the Frosting, beat spread and vanilla in large bowl with electric mixer on medium speed until light and fluffy. Mix confectioners' sugar and cocoa powder. Gradually add to spread, beating until well blended after each addition and scraping sides and bottom of bowl frequently. Add reserved coconut milk; beat until light and fluffy. Fill and frost cooled cake with Frosting.