sauce adapted from Everyday Food
For the beans:
1 lb dried pinto beans
1 28-oz can diced tomatoes
1 yellow onion, roughly chopped
2 ancho peppers, stemmed, seeded, and torn into strips
1 large chipotle in adobo
1/2 cup almonds, toasted (pre-sliced almonds will make a smoother puree)
1/4 cup raisins
3 oz dark chocolate, chopped
3 garlic cloves, peeled
3 TBSP olive oil
3/4 tsp ground cumin
1/2 tsp ground cinnamon
2 cups water
fine sea or kosher salt, to taste
For the relish:
yields about 2 cups
1/4 cup packed cilantro, chopped finely
2 scallions, white and tender green bits, very thinly sliced
1/2 medium jalapeno, very thinly sliced
1/4 tsp fine sea or kosher salt, or to taste
juice of half a lime
1 medium-large cucumber, seeded and cut into 1/4-inch thick, 1 1/2-inch long baton
Fresh soft corn tortillas (see note above recipe head) or store-bought soft corn tortillas, warmed in a stack in the oven
To make the beans, add the dried beans to a large slow cooker and pour in enough water to cover by a few inches. Cover with a towel and let soak overnight.
Drain and rinse the beans, then return them to the slow cooker and set aside. In a food processor, combine the sauce ingredients from tomatoes through cinnamon. Process until smooth, a couple of minutes, scraping down the sides as needed. Transfer to the slow cooker, add the 2 cups water, and stir well.
Cook on low for 10 hours. At 8 hours, the sauce will still be a bit too thin, so plan to let them cook for the entire 10 hours to thicken appropriately and for the beans to tenderize thoroughly. At 9 1/2 hours, check the beans to make sure they're tender, then add salt to taste. Replace the cover and set aside while you prepare the relish.
Stir together the cilantro, scallions, jalapeno, salt, and lime juice. Add the cucumber and toss gently until thoroughly combined. Adjust salt, if needed, and let sit until mellowed a bit, about 20 minutes, while you make tortillas. Assemble and serve the tacos as soon as the tortillas are ready.