Add oil to pressure cooker, and heat on Saute. Add onion and garlic, and saute a few minutes, until fragrant.
Add all remaining ingredients, and stir to combine.
Seal the pressure cooker, and set to 45 minutes, on high.
Once the timer ends, allow the pot to naturally release pressure for 25 minutes, then manually release any remaining pressure.
Drain the beans, reserving the liquid.
Return the beans to the pot. Use an immersion blender to roughly puree the beans, adding the reserved cooking liquid to achieve the desired consistency. Alternatively, you can use a food processor or potato masher instead of an immersion blender.