Add butter and sugar to large mixing bowl. Using a hand mixer, “cream” together butter and sugar until light and fluffy. Then add eggs and vanilla and mix until fully incorporated. Next, add spices and mix until fully combined.
Add carrots to bowl and mix together with a rubber spatula. At this point, the mix will look like it has curdled, but it hasn’t.
Add flour to bowl and mix gently with a rubber spatula until fully combined, making sure to scrape the edges of the bowl.
Spray a 7×3 cheesecake or springform pan with nonstick cooking spray. Pour batter into pan and spread out as evenly as you can. Cover pan with foil to keep out condensation.
Add 3-inch trivet and 1 ½ cups water to cooker. Place pan on top of trivet. Lock lid and cook for 60 minutes at high pressure.
Once cook time is complete, allow pressure to release naturally for 10 minutes. Then quick-release remaining pressure. Remove pan from cooker and uncover. Allow to cool for 10 minutes before removing from pan. Then allow cake to cool to room temperature before icing.
Meanwhile… Add cream cheese, butter, vanilla extract, and salt to mixing bowl. Using a had hand mixer, whip until fully combined.
Then add powdered sugar ½ cup at a time, blending completely before adding more.
When it's time to add the frosting to the cake, place big spoonfuls in the middle of the top of the cake. Then gently spread outwards. Since the frosting is so soft, you should be able just let it fall over the sides.
Once the cake is iced, place in the fridge for 30 minutes so that the frosting sets.
Once you add the flour, I recommend not mixing with a mixer of any kind beyond that point, but rather a rubber spatula. While you can definitely get away with this when baking in an oven, due to the way Instant Pots bake things, you'll want to minimize anything that can make the texture more dense or chewy. Well, the more you mix flour, the more gluten is developed. So, for this reason, I prefer to hand mix cakes before cooking in the IP.This frosting is very soft! So when icing your cake, the frosting will pretty much spread itself. I didn't even touch the sides of the cake. I simply spread the frosting over the edges and let gravity do the work. And then, once frosting was down the sides, I set the cake in the fridge for about 30 minutes so that it would set and not continue spreading. Please note that I live in Florida and cooked this cake on a summer day, so you may not have that same issue; just something to be aware of.
Cooking something for 60 minutes seems like a long time! Well, if you were boiling this cake in the liquid, 60 minutes would be way overboard. But with this method, the pan is sitting on top of an elevated trivet, so you're not boiling it, you're steaming it.Why is the cook time so long? When "baking" in a pressure cooker, what you're actually doing is steaming with wet heat, rather than baking with dry heat. The temperature inside of a pressure cooker will reach 212 degrees F, which is significantly lower than what you would set your oven (around 400F). Can I use store-bought matchstick carrots? No. While matchstick carrots are very thin, they are not nearly fine enough for use in a carrot cake and may yield crunchy carrots inside the cake. I recommend using the smallest grater (other than a microplane) that you have. And while you can you a food processor, they often leave larger pieces.Why not just use the oven? There are many ways to answer this question (eg. I'm living in a camper, my oven is broken, it's too hot outside, etc.). But my new favorite answer is this: because I like cooking in my pot! And I can!