Place a steamer basket in the bottom of the pressure cooking pot and add 1 cup water. Place the pear quarters and blueberries inside the steamer basket. Lock the lid in place. Select Pressure Cook or ManualHigh and 4 minutes cook time.
When the cook time ends, turn off the pressure cooker and use a quick pressure release. When the float valve drops, carefully remove the lid.
Remove the pears and blueberries from the steamer basket, reserving the cooking water. Allow to cool for 20 minutes.
Transfer the cooked pears and blueberries to a blender jar or food processor. Add the peeled banana and 1/4 cup reserved cooking water and blend until very smooth. (Add more cooking water if needed to blend but use the minimum amount necessary.)
TIP: You can use fresh or frozen blueberries in this puree without adjusting the cook time.