Preheat oven to 400. Grease a 9 x 13 pan.

In  large bowl, mix together sugar and flour.

In pot, melt butter. Add cocoa and coffee and heat until boiling. Remove from heat. Pour over sugar/flour mixture. Stir well.

Mix eggs, buttermilk, baking soda and vanilla in large measuring cup. Stir into cocoa mixture.

Scrape into greased pan and bake for 20-25 minutes.

While cake is baking, prepare frosting. Melt butter in large bowl in microwave. Whisk in cocoa, milk and vanilla. Add powdered sugar and beat well. Spread over cake while both are still warm.

To test if cake is ready, insert a toothpick or cake tester. It should come out with tiny crumbs sticking to it and the sides of the cake should be pulled slightly away from the edge of the pan. Sprinkle with chocolate chips.

Now pour and smooth icing over the top. Chips will melt into the frosting and cake. If needed to get frosting to spread well, place cake back in turned off oven for about 5 minutes. Spread again if needed. Take out and place on rack. Let cool. Frosting will harden as it cools.