In a large bowl mix together the almond flour, coconut flour, sweetener, baking powder, and cocoa powder. Use a fork or whisk to break apart any clumps.
Next mix in the softened butter, vanilla, and coconut milk. Mix the batter until smooth then taste the batter to see if you need to add any more sweetener to meet your taste.
Mix the eggs into the batter.
Grease an oven safe pan that fits inside of your pressure cooker with coconut oil or butter. Pour the batter into the pan and smooth out the top.
In a separate dish whisk together all the ingredients for the hidden sugar-free chocolate sauce.
Pour the chocolate sauce over the cake batter. A spoon can be used to soften the pouring so that the sauce doesn't create holes in the batter. The recipe video will help you see this technique.
Cover the pan with foil. Add 2 cups of water to the bottom of the pressure cooker insert. Place a trivet at the bottom of the pressure cooker and carefully lower the cake to rest on top of the trivet.
Close the lid on the Instant Pot and turn the pressure valve to seal. Cook the cake on high pressure for 30 minutes using the "manual" or "pressure cook" setting. Release the pressure using the quick release method.
Turn off the Instant Pot, open the lid, and remove the cake. Remove the foil off the cake and let it cool on the counter for 5-10 minutes. Serve the cake while it is still warm topped with whipped cream.