Heat oven to 350°F. Grease and flour 2 (9-inch) cake pans; line bottom of pans with parchment or waxed paper; set aside.
Combine flour, cocoa, baking soda, salt and 1/2 teaspoon cinnamon in bowl; set aside.
Combine sugar, 1/2 cup butter and oil in bowl. Beat at medium speed, scraping bowl often, until creamy. Continue beating, adding egg and vanilla, until well mixed. Gradually add flour mixture alternately with buttermilk and coffee, beating at low speed until well mixed.
Spoon batter evenly into prepared pans. Bake 30-32 minutes or until toothpick inserted in center comes out clean. Cool 10 minutes. Remove from pans. Cool completely. Remove parchment paper.
Combine chocolate, 1/2 cup whipping cream, 1 tablespoon butter and corn syrup in saucepan. Cook over medium heat until chocolate is melted. Refrigerate 1 hour or until thickened.
Beat remaining 1 1/2 cups whipping cream in bowl at high speed until soft peaks form. Add powdered sugar and 1/4 teaspoon cinnamon; continue beating until stiff peaks form.
Place 1 cake layer on serving plate. Spread chocolate mixture over cake layer. Spread 1 cup whipped cream mixture over chocolate mixture. Top with remaining cake layer; frost with remaining whipped cream mixture. Store refrigerated.
*Substitute 1 tablespoon vinegar or lemon juice and enough milk to equal 1 cup. Let stand 5 minutes.