4 cups unsalted chicken stock 2 cups dried Great Northern beans (unsoaked) 2 cups chopped white onion (about 8 oz.) 1 1/3 cups tomatillo salsa (such as Frontera) 1/2 cup water 2 teaspoons ground cumin 1 teaspoon dried oregano 1 teaspoon kosher salt 8 garlic cloves, minced 2 pounds trimmed boneless pork shoulder, cut into 1 1/2-in. cubes (about 2 1/2 lb. purchase weight) 1/2 cup thinly sliced green onions 1/2 cup thinly sliced radishes (optional)