Preheat the oven to 325 F (160 C).
Grease a 12-cup, non-stick bundt pan and dust with cocoa powder. Be sure that all ridges and creases are well covered.
In a large bowl whisk together the flour, cocoa, baking soda and salt. Set aside.
In a very large bowl beat the butter and sugar until fluffy. This should take around 5 minutes.
Beat in the eggs 1 at a time. Turn off the mixer and scrape down the sides and bottom of the bowl a few times.
With the mixer on low speed, beat in about ½ of the flour mixture, followed by the sour cream. Then beat in the rest of the flour mixture.
Add the instant coffee powder to the boiling water.
Very carefully mix the hot water into the cake batter.
Spoon the batter into the prepared pan and smooth the top.
Bake in the preheated oven for 65-75 minutes, or until an inserted toothpick comes out clean or with a few dry crumbs sticking to it. You may see a large crack around the top - this is normal and expected.
Remove from the oven. Cool in the pan for at least 30 minutes. Then very carefully invert the pan and continue cooling on a wire rack.