Slice the tops off of your apples and core the apples without cutting through to the bottom. Scoop out a little extra of the flesh so that you have room for your apple pie filling.
Combine the walnuts, brown sugar, and pumpkin spice in a bowl.
Divide the filling mixture evenly between the apples.
Add 4 cups of water to your pressure cooker. Insert your steamer basket and place the apples on top.
Top each apple with 1 tbsp of butter. This may seem like a lot, but it will melt and mix with the brown sugar and taste delicious.
Seal your pressure cooker and cook on high for three minutes. The skins of the apples may crack during this time, but I personally didn't mind, nor did I find it affected the flavor.
When the three minutes are up, do a quick release. This should take a minute or so.
Serve warm (with optional whipped cream and a few pomegranate arils, if you fancy) and enjoy!