Heat oil in a sauté pan over medium heat and sauté onions for 4 minutes.
Add chopped garlic and sauté an additional minute.
Place the onion garlic mixture into the crock pot along with the rest of the ingredients and stir to combine.
Cook on low for 8-10 hours or high for 4-5 hours.
Using either a hand blender or traditional blender, puree the ingredients to your desired texture (I like to get it so a few pieces of beans are still visible so the soup is thick and still has a bit of texture).
Top with a dollop of yogurt, sour cream, crème fraiche and/or cilantro.