Pick through the beans and remove any debris; remove any beans that have split and/or beans with holes. Rinse beans. Place beans in a dutch oven. Cover beans with water. Let beans soak overnight.

When ready to prepare beans, rinse beans and cover again with cold water, add 1 teaspoon baking soda. Bring beans to a boil; boil for 2 to 3 minutes. Drain beans, reserving water.

In a large skillet. heat oil over medium heat; sauté onion and serrano pepper just until the onions begin to brown and the chili blisters, about 4 minutes.

Add the crushed garlic. saute until it softens.

In an earthen bean pot add: beans, onions, serrano pepper and garlic. Pour in enough reserved bean water to cover the beans by 3 inches. Cover the pot tightly.

Bake at 350º for 2 to 4 hours or until beans have softened.

Check beans often to make sure the pot has enough water. Add more reserved bean water if necessary. Once the beans are soft and you can squeeze a bean between you fingers, allow to bake, uncovered, for an additional 15 to 30 minutes. Taste and adjust the salt if needed. Leave enough broth in the bean pot, in case you want to mash the beans for refried beans.