Make sure that you thoroughly cook dried beans for best texture. For a splurge, add a layer of guacamole between the bean and cream cheese layer.

Two days before you serve the dip, sort the pinto beans, removing any foreign objects. Rinse the beans thoroughly and cover with 10 cups cold water. Cover and let stand overnight. In the morning, drain the beans and place in a 2-quart slow cooker with the onion. Add 3 cups water, cover, and cook on low for 8–9 hours until tender.

Test to see whether the beans are tender. If necessary, drain the pinto beans, reserving ¼ cup of the cooking liquid. Place the beans and onions in large bowl with the salt and chili powder. Using a potato masher, mash the beans, leaving some whole. Add reserved cooking liquid as needed until a spreading consistency is reached.

In another medium bowl, beat cream cheese until softened. Add sour cream and chiles; mix until blended.

On a large platter, spread the pinto bean mixture. Top with the sour cream mixture, leaving a 1-inch border of the bean mixture showing around the edges. Top with lettuce, tomato, and cheese. Serve immediately or cover and chill up to 2 days. Serve with taco or tortilla chips.