German Sauerbraten Stew Recipe

2 pounds boneless pork, trimmed and cut into 1-1/2-inch cubes 2 tablespoons vegetable oil 1-1/2 quarts water 2 cups ketchup 1 large onion, chopped 2 medium potatoes, peeled and cubed 3 medium carrots, cut into 1/2-in slices 1 cup fresh or frozen cut green beans (1-inch pieces) 1 cup shredded cabbage 2 celery ribs, cut into 1/2-inch slices 1/4 to 1/2 teaspoon ground allspice 1/4 teaspoon pepper 1 cup crushed gingersnaps (about 16 cookies)