8 slices (about 1/2 lb.) Llano Seco Bacon, chopped (ham or ham hock can be substituted)
2 onions, chopped
2 garlic cloves, minced
1/2 cup tomato purée
1/2 cup canned red chiles, or dried mild chiles of your choosing, rehydrated a few hours in water.
1 tbsp firmly packed brown sugar
1 tbsp stone-ground mustard
1 tsp salt
Pick over and rinse beans. Put in a 6-qt. pot and cover with water. Bring to a boil, cover, take off heat, and let stand 1 hour.
Drain beans. Cover with fresh water and bring to a boil. Lower heat to a simmer, and cook, covered, until tender, anywhere from 40 to 60 minutes. Drain, reserving 1 cup cooking liquid along with beans.
In a 5-qt. pot over medium-high heat, cook bacon until crisp, stirring a few times. Pour off all but 1 tbsp. fat from pan.
Add onions and garlic and cook, stirring, until onions just start to brown, about 4 minutes.
Add tomato purée, red chiles, brown sugar, mustard, salt, beans, and reserved cooking liquid.
Bring to a low boil, stirring often; then lower heat and simmer for about 30 minutes to blend flavors.