To make the bottom cake layer: Preheat the oven to 350°F and grease a 6- or 7-inch springform pan with coconut oil. Wrap the bottom with foil to prevent spillage. Set aside.
In a medium bowl, combine the almond flour, coconut f lour, baking soda, cinnamon, and allspice. Set aside.
In a large bowl, using a hand mixer, mix the coconut oil and sweetener until combined. Add the eggs, almond milk, and vanilla, and beat just until combined.
Add the dry ingredients and mix just until combined. Gently fold in the carrots.
Transfer the batter to the prepared pan and bake for 20 minutes, or until a toothpick inserted into the center comes out clean. Allow to cool to the touch before adding the cheesecake layer. While the cake is cooling, make the cheesecake layer.
Note: The bottom layer can be made ahead and refrigerated or frozen until ready to use.
To make the cheesecake layer: In a large bowl, using a hand mixer, beat the cream cheese and sweetener until smooth. Add the vanilla, sour cream, coconut cream, and egg, and mix until just combined and smooth in consistency. (Do not overmix.)
Pour the mixture into the pan, over the cooled bottom cake layer and cover securely with foil.
Pour 1½ cups water into the Instant Pot and place a steamer rack or trivet in the bottom. Place the cheesecake on the rack.
Secure the lid on the Instant Pot and move the vent knob to the sealed position.
Select “Manual” and cook on high pressure for 30 minutes. Once the cooking time is up, let the steam release naturally.
Remove the cake from the Instant Pot and leave covered for about 30 minutes before removing the foil. Let it sit for another hour, uncovered before refrigerating it still in the springform pan for 4 hours.
When the time is up, remove the cheesecake from the pan and serve with the optional topping.
To make the optional topping: With a spoon, mix the cream cheese, vanilla, coconut cream, and sweetener in a small bowl. Microwave on high for 10–15 seconds to make the topping pourable. Pour onto the cooled cheesecake and using a knife, spread into a thin layer. Top with walnuts.