PREP: For a quicker prep, give the onion and pepper a quick coarse chop and add along with the jalapeños (be sure to remove the ribs and seeds before adding if concerned about heat) and garlic to a food processor and pulse to chop.
BACON: Thinly slice the bacon into 1/2 inch pieces. Add to a large cast iron skillet and cook, over medium-high heat, stirring regularly, until the bacon begins to brown and the fat is rendered. Use a slotted spoon to remove all the bacon from the skillet to a paper-towel-lined plate. Leave the bacon grease in the pan and keeping the heat at medium-high, add in the diced onion and pepper. (If you added all the veggies to the food processor, just add them all in here!) Cook, stirring occasionally, until softened, about 7-9 minutes.
VEGGIES: Add in the minced garlic and jalapeños. Stir until fragrant, 1 minute. Add in all the seasonings and cook for 1 minute. Finally, add in the crushed tomatoes (undrained), and cook for one more minute, scraping the bottom of the pan to release any browned bits. Use a spatula to scrape every bit of this mixture into a slow cooker or instant pot.
ADD BEANS AND COOK: Rinse the beans in a strainer and pick through them, discarding any debris or pebbles. Add the rinsed beans, chicken stock, and water to the slow cooker or instant pot. Add in the cooked and reserved bacon. Finally, season (to taste) with salt and pepper. ( I add 2 teaspoons fine sea salt and 1/2 teaspoon pepper, but add to preference.) Stir everything together. Cover and cook on high for 7-9 hours in the slow cooker or until beans are very tender (this is 8 hours in my crockpot). INSTANT POT: Seal the pot turn and cook on manual mode for 45 minutes (it takes about 15-20 minutes to get to pressure). Once finished, allow for a natural release for 25 minutes before releasing the rest of the pressure manually.
BLEND PORTION OF BEANS: See Note 3. Once the beans are tender, remove 3 cups of the beans and liquid and add to a powerful blender. Blend until smooth, stirring as needed in between blending (if needed, add more liquid from the slow cooker or instant pot to more easily blend). Pour blended beans back into the slow cooker and stir.
FINISHING: Taste and adjust seasonings. (I typically add another 1/4 teaspoon up to a full teaspoon fine sea salt here-- it really just depends on how salty the chicken stock used is; add slowly until flavors sing.) Add optional cilantro and stir through. Serve as a side dish (See Note 2) or use in another recipe. Beans will continue to thicken as they sit and become more flavorful as they're stored in the fridge overnight.