Grease a cake pan with butter (7in for 5.7L Instant Pot)
In one bowl, combine the flour, cocoa powder, baking powder, and salt.
In another bowl, combine the eggs, sugar, melted butter, vanilla, and espresso.
Gently whisk the dry mixture into the wet mixture then fold in the chocolate chips.
Pour the mixture into the prepared pan and cover with aluminium foil.
Pour 300ml water into the inner pot and place the springform pan on top of the trivet inside.
Select Bake (high) or Pressure Cook button and set the cook time for 35 minutes and press start.
When the cooking program has finished, let the pressure release naturally for 15 minutes, then quick release any remaining pressure.
Carefully remove the pan from the Instant Pot, remove the foil, and let the cake cool completely.
Once cooled, dust the cake with cocoa powder and serve with vanilla ice cream.