Mix instant coffee with water set aside for later. Sift flour, cocoa powder, baking soda and baking powder together taking care that all the components are well combined and evenly distributed. In the bowl of a stand mixer, mix the butter and shortening with paddle attachment on 2nd speed until combined. Add sugar, sour cream, vanilla extract, coffee mixture, and salt starting on 1st seed and gradually moving to 2nd speed until light and fluffy (approximately 8 minutes). At 1 1/2 speed add the whole eggs, in small amounts, until smooth and fully incorporated. Add dry ingredients and banana puree in staggering steps to the mixer and blend until well combined.
Pour into greased sheet pans or 4 (4 by 13-inch round cake pans and bake for 30 to 45 minutes or until a toothpick inserted into the center of the cake comes out clean.
This recipe was provided by professional chefs and has been scaled down from a bulk recipe provided by a restaurant. The Food Network Kitchens chefs have not tested this recipe, in the proportions indicated, and therefore, we cannot make any representation as to the results.