Place everything in the crockpot and stir to combine. Cook on High for 6-8 hours. (Mine were done by 6 hours but dinner wasn't ready, so I left them in there-you're just going to mush them up anyway) :) If the liquid seems low while you're cooking, just add a little extra chicken stock or water.
Once the beans are cooked, remove the onion, strain them and reserve the liquid. Use a potato masher to smash them into gooey bits. Add the reserved water to get the consistency you want. Serve hot and topped with onions, cheese, sour cream, in a tortilla, use for bean dip...you get the idea. :)
To cook in the Crockpot Express (or other pressure cooker)
Add all the ingredients to the pot, press Beans/Chili and adjust time to 50 minutes. Allow a natural pressure release when cook time is up. Transfer to another bowl and follow instructions above for mashing.
Store beans in an airtight container in the refrigerator. You can also freeze them in one cup portions for use later!