In a medium bowl, whisk together the almond flour, cocoa powder, sweetener, and salt. Stir in the melted butter, egg, and vanilla extract until the dough comes together. If it's too dry, add water a tiny bit at a time.
Gather up the dough into a ball and place on a silicone mat or large piece of parchment paper. Top with another piece of parchment and roll out to less than 1/4 inch thick.
Use a 1-inch cookie cutter to cut out 11 little circles for decorating the top of the cake. Lift and place around the mat or parchment. Transfer the whole mat or parchment to a large baking sheet.
Bake 20 minutes or so, until dry-ish and firm to the touch. Turn off the oven and let cool inside.
Lightly grease the bottom and sides of a 7-inch springform pan.
In the same bowl from the crumble, whisk together the almond flour, cocoa powder, and powdered sweetener. Stir in the butter until well combined.
Press firmly and evenly into the bottom of the prepared baking pan.
In a large bowl, beat the cream cheese until smooth. Beat in the sweetener until well combined, then beat in the heavy cream and vanilla.
Beat in the egg and the remaining egg from the cookie crumble until just combined. Break up the crumble into small pieces, reserving the circles for decorating. Fold most of the cookie crumble into the filling mixture, reserving some for the top of the cake.
Pour the filling over the crust and spread to the edges.
Wrap the bottom of the springform pan tightly in a large piece of foil. Place a piece of paper towel over the top of the springform pan (not touching the cheesecake) and then wrap foil around the top as well. Your whole pan should be mostly covered in foil to keep out excess moisture. Make sure the foil fits tightly.
Place the rack that came with your Instant Pot or pressure cooker into the bottom. Pour a cup of water into the bottom. Carefully lower the wrapped cheesecake pan onto the rack (there are ways to do this with a sling made out of tin foil but I didn't bother with that).
Close the lid and set the Instant Pot to manual mode for 35 minutes on high. Once the cooking time is complete, let the pressure to release naturally (do not vent it).
Lift out the cheesecake and let it cool to room temperature, and then refrigerate for 3 or 4 hours, or even overnight.
To release the sides, heat up a knife by holding it over a gas stove flame for a few seconds or by running some boiling water over it. Run the knife around the inside edge of the pan to loosen.
Topping and decorating
Whip the cream and the sweetener until the cream holds stiff peaks. Spread over the top of the cake, saving some to pipe decorative rosettes, if desired.
Use the cut out circles to decorate each slices and one for the middle of the cake. Any remaining cookie crumble can be sprinkled over top.
No need to wrap the pan in foil.
You may also want to bake the bottom crust for 10 minutes at 325F to help it firm up.
Bake the cheesecake at 300F for at least 30 minutes. Check on it every 5 minutes after that. Because I did not try this in the oven, I can't tell you exactly how long it will take to bake.
The edges should be set but the center should still jiggle slightly when the pan is shaken.