Gather ingredients and tools.
Prepare the bundt pan and cake bite pan by spraying liberally with baking spray.
In a small sauce pan, heat the Guinness and butter until simmering.
Remove from heat and add cocoa powder, stirring with a silicone whisk.
Stir until very smooth. Set aside to cool.
In a medium-sized mixing bowl, combine the flour, sugar, baking soda, and salt. Stir with wire whisk to combine. Set aside.
In the bowl of your stand mixer, with scraper paddles attached, add eggs and creme fraiche. Mix well to combine.
Pour in the cooled guinness-chocolate mixture.Note: make sure the chocolate mixture is cool, otherwise you will curdle the egg mixture.
Stir just until it is combined. Do not over-mix.
Add the flour mixture in to the bowl and mix only a few turns, until it is combined, but still lumpy. Again, do not over-mix!
Remove bowl from mixer and turn it over with your spatula, scraping up from the bottom to make sure it is all combined. Mixture will be thick and slightly lumpy.
Carefully fill the bundt pan to roughly 2/3 full. You will have batter left-over.
Cover the bundt pan with foil, puffing it up so that it gives the cake room to grow underneath. (Don't wrap tightly.) Set the pan on the sling.
Add a cup of water to the inner pot of your Instant Pot. Set the sling in the pot. Close the lid, and turn the vent to sealing.Cook on manual, high for 27 minutes. When the time is up, let the pot release pressure naturally for 10 minutes, and then carefully turn the vent to open, releasing the remaining pressure.
While the cake is cooking, use the remaining batter to fill the cake bites. Divide the batter evenly between the bites.
Remove the cake from the pot, and remove the foil. Let cool in the pan for a few minutes.
If the cake has risen above the pan, you can use a knife to slice across the top to make a flat base. Turn the cake out of the pan onto a cooling rack by placing the rack upside down on the cake pan, then flipping the two over together. Remove the cake pan.
Place your cake bite pan, covered with foil, on the silicone sling. Make sure there is still some water in the bottom of the inner pot, and place the cake bites in the pot.Cook the bites on manual, high for 7 minutes. Let the pressure release naturally until the pin drops. Then remove the bites and let cool on the rack with the cake.