Prepare your 6-cup Bundt pan by greasing the inside really well with butter or shortening and coating with cocoa powder or spray well with Baker’s Joy (which has flour in it, don’t use regular spray coating). Set aside.
In a large mixing bowl on high speed mix together the softened butter and eggs until smooth, 2-3 minutes.
Add the cake mix, sour cream and milk. On slow speed mix until starting to combine and then increase the mixer speed to high and beat for 2 minutes.
Pour the batter into the Bundt pan to about half an inch from the top of the pan.
Lay a paper towel over the top of the pan. Next place a piece of heavy duty foil over the top of the pan. Don’t pull it down tight, almost leave like a little puff tent in the middle. Pinch the foil around the edge of the pan to seal.
Place 1 ½ cups of water into the bottom of your Instant Pot.
Set the covered Bundt pan onto the handled trivet that came with your Instant Pot and lower into the Instant Pot using the trivet handles.
Place your Instant Pot lid on and set the vent valve to SEAL.
Hit the Manual button and high pressure and set the time for 35 minutes.
Now make your ganache (see instructions below).
At the end of the 35 minutes when the Instant Pot beeps put a towel over the vent valve and release the steam. Once all the steam has been released and the safety pin by the vent valve has dropped you can open the lid.
Carefully remove the Bundt pan using the handles and a towel (because it will be hot still).
Let the cake sit for about 5 minutes and then remove the foil and paper towel.
Place your cake plate on top of the Bundt pan and give it a quick flip over to release the cake onto the pan.
Pour the thickened ganache over the top of the cake.