Pulse the gingersnap cookies in a food processor or blender until finely ground. Or crush them in a ziplock bag with a rolling pin.
Add melted butter and brown sugar, pulse until well combined. Divide the crumb mixture between 7 Mason jars, press it with the back of a spoon. Do not press it too hard. You may skip the crust for a crustless pumpkin cheesecake instead.
.In a medium mixing bowl, beat the cream cheese and brown sugar on low speed with a hand blender. Scrape down the sides of the bowl with a spatula and continue beating on low speed until smooth.
Add the egg and beat on medium-low speed until well incorporated.
Add the pumpkin purée, sour cream, pumpkin pie spice mix, vanilla extract, salt and blend until well mixed.
Pour about 4 tbsp of the pumpkin cheesecake filling in the prepared gingersnap crust in each jar. Give it a gentle tap to eliminate any bubbles.
Cover the jar with the lid that has the rubber ring, then close the jar using the outer band, but do not tighten the lid all the way, just enough to cover the jar in order to prevent any condensation from dripping in it.
Add 1 cup of water into the inner steel pot of the Instant Pot. Place a trivet and stack the jars offset on the trivet as shown below.
Close the lid of the Instant Pot, and set the valve to 'SEALING'. Pressure cook on 'HIGH' for 6 minutes. It will take some time for the pressure to build up after which the timer will start.
Let the pot depressurize naturally, once the silver pin drops, turn the knob to 'VENTING' and open the lid.
Transfer the jars to a wire rack with the help of tongs. Let the cheesecake cool completely at room temperature, then refrigerate for another 5-6 hours. These cheesecake jars will last well up to 5 days in the refrigerator.
Top Mason jar pumpkin cheesecake with cool whip or homemade whipped cream, gingersnap cookie crumbs, and some dulce de leche or caramel sauce.