Combine chili powder, mustard, 1/2 teaspoon salt, and 1/4 teaspoon pepper; rub mixture onto the pork. Cover and chill overnight.

Rinse the beans. Place in a large pot with 3 cups water. Cover and let soak in a cool place overnight. Drain and rinse the beans.

In a large saucepan cook the bacon until crisp. Drain fat. Add garlic and cook for 1 minute more. Add the beans, 1/2 teaspoon salt, and 3 cups fresh water. Bring to boiling; reduce heat. Cover and simmer for 60 minutes or until beans are tender. Drain beans; stir thyme into beans. Cover and set aside.

In a 10-inch ovenproof skillet heat cooking oil over medium-high heat. Add the pork. Brown pork on all sides. Drain off any excess fat. Carefully add beef broth to the skillet. Transfer skillet to a 450 degree F oven. Roast, uncovered, for 20 minutes or until an instant-read thermometer inserted in pork registers 160 degree F. Remove from oven. Transfer pork to a cutting board; keep warm.

Whisk 1 tablespoon of the butter into the pan juices in skillet. Transfer to a small bowl; set aside.

In the same skillet, heat the remaining 1 tablespoon butter over medium heat. Add the spinach and cook and stir until wilted, 1 to 2 minutes. Season with salt and pepper.

To serve, slice the pork. Arrange beans in the center of the serving plates. Spoon spinach on top of beans. Spoon some of the pan juices around beans on plate. Arrange pork on top of spinach. Pass remaining pan juices. Makes 4 servings.