Preheat oven to 170 °Celsius.
Mix instant coffee powder with hot water. Add to milk and leave aside to cool.
In a separate bowl, beat butter and sugar till soft and creamy for approximately 2 minutes. Add eggs, one at a time, beating well after each addition.
In another separate bowl, sift flour, baking powder and salt. Fold in the sifted ingredients into the creamed mixture alternately with the coffee mixture, starting and ending with flour.
Pour the batter into two well greased and floured cake tins. Level the top and bake the cakes for 45 to 50 minutes or until a skewer inserted in the center of the cakes come out clean.
Remove cakes from oven and let them cool completely before decorating. Baking time may vary slightly for larger cakes.
To make the coffee buttercream, dilute the coffee powder in hot water, in a large bowl. Let the coffee cool down to room temperature.
Add in the shortening, butter and sugar. Beat light the icing turns light and fluffy.
Fill the cake layers with the coffee buttercream and cover the sides of the stacked cake with the remaining buttercream.
Decorate with the coffee flavored chocolate chips.