Thoroughly rinse the beans in a strainer, being sure to remove any stones or damaged beans.
Turn your Instant Pot on Saute mode, then add the bacon grease and onion and saute until the onion is translucent. Add the garlic in and cook for 30 seconds, then turn of the heat.
Add the water, chicken stock, taco seasoning, salt, bay leaf and rinsed beans to the Instant Pot and stir to combine.
Put the lid on your Instant Pot and cook on high pressure (or Bean mode) for 60 minutes, then allow the pressure to release naturally. When the pressure is released, remove the lid and throw away the bay leaf.
Strain the liquid into a bowl, reserving it. Don't toss it!
Mash the beans and slowly add the reserved liquid back until you get the consistency you like. They'll keep getting thicker as they cool. I use an immersion blender to make my beans smooth, but still have texture.
Serve your refried beans as a side dish with your favorite Mexican dinner.
Sprinkle with shredded cheese and other toppings before serving, if desired.