Grease a 15cm (7-inch) springform tin with butter and add parchment paper to the base if available.
Add the cocoa, baking soda, flour and sugar to a bowl. Mix together.
In a separate bowl melt the butter in the microwave and then add the eggs, sour cream, vanilla extract and water. Whisk together with an electric whisk.
Add the wet ingredients to the dry and fold together until well combined.
Add the mixture to the springform tin and spread out evenly. Cover the tin with tin foil.
Add 200ml of cold water to the instant pot and then put the trivet in place.
Make a sling using foil and put the springform tin into the instant pot.
Put the lid on and set at manual, high pressure for 35 minutes.
Allow to remain under pressure for around 15 minutes and then do a quick release.
Remove the springform tin using the sling.
Serve and enjoy!