Preheat oven to 180 C / Gas 4. Grease two 23cm round cake tins.
Measure flour, sugar, cocoa, oil, eggs, buttermilk, baking powder, bicarb and salt into a mixing bowl. Dissolve instant coffee in hot water, and add to mixing bowl. Beat at medium speed for 2 minutes until smooth; mixture will be thin. Pour into prepared tins.
Bake for 30 to 35 minutes, or until a skewer comes out clean. Cool in tins for 10 minutes, and then turn out onto racks to cool completely.
Ice cooled cake with Coffee Icing. After icing, melt some plain chocolate in a double boiler. Drizzle chocolate around top outside edges letting it run down sides, or over top of cake.