Scrub the outside of the kabocha squash well under running water.
Place a silicone rack in the bottom of the IP.Add the water. If using a 6 quart Instant Pot add 1 cup of water. If using a 8 quart Instant Pot add 1 ½ cups of water.
Place the lid on the IP and turn the vent to the sealing position.
Press the manual button and set the timer for 20 minutes for a 5 lb kabocha squash.
If pressure cooking a smaller squash reduce the pressure cooking time accordingly. For example if cooking a 3-4 pound squash cook for 15 minutes. If cooking a kabocha squash that is 2 lbs. or smaller cook for 10 minutes.
Once the pressure cooking time is done quick release the steam by sliding the pressure valve to the venting position.
Remove the lid venting the steam away from your face.Allow the steam to dissipate.
Lift the kabocha squash up with the silicone handles.
Place the squash on a cookie sheet or in a bowl to cool.
Once the squash has cooled enough for you to handle it safely pull the skin away from the flesh.
Cut the squash in half and use a spoon to scoop the fibers and seeds from the inside of the squash.
Scoop the cooked flesh of the kabocha squash from the skin and place in a bowl.
Mash the squash and store in the refrigerator until ready to use.