Grease 3 9"-pie pans (if you only have 1-2 pie pans, refrigerate batter, while baking). Line the bottom of each cake pan with parchment paper; dust with unsweetened cocoa powder. Set prepared pans aside
In a small bowl, stir together egg, buttermilk, and vegetable oil; set aside. In large mixing bowl, stir together,flour, sugar, 1/2cup cocoa powder, baking soda, and salt. Gradually add the buttermilk mixturee to flour mixture, beating with an electric mixer until combined. Gradually beat in hot coffee. Pour batter into prepared pans (layers will appear shallow).
Bake in 350 degree oven 22-25 minutes or until toothpick inserted near center comes out clean. Cool cakes in pans on wire racks for 10 minutes. Loosen sides from pans, then invert cakes on racks. Remove the cake layers from pans. Peel off paper; cool thoroughly.
When the cakes are cool, make the chocolate frosting. Place one cake layer, top side down, onto a serving plate with a lip(to catch excess icing). Using an icing spactula or wide knife, work quickly to frost the top layer this layer with one-third of the frosting. Arrange one-third of the pecans on top and drizzle with some of the carmel ice-cream topping. Repeat with the frosting, pecans, and carmel topping. Top with the third layer, top side up. Repeat with remaining frosting, pecans and carmel topping. Chill cake 1 to 2 hours before serving.
Chocolate Frosting: In a medium saucepan, stir together 1 cup sugar and 1/2 cup milk. Add 6 tablespoons of butter, cut up. Bring mixture to boiling, stirring constantly. Remove from heat. Add one 12 ounce package semisweet chocolate pieces (2 cups). Using a wire whisk, mix until smooth. If frosting is grainy or too thick, add 2 teaspoons hot coffee. If necessary, let stand several minutes before using. Makes about 2 1/2 cups of frosting, enough for this cake.
How to make sour milk: Don't have buttermilk? Substitute sour milk. For 1 cup of sour milk, place 1 tablespoon of lemon juice or vinegar in a glass measuring cup. Add milk to make one cup, let stand 5 minutes before using.