Green Soup with Ham

Name: Green Soup with Ham
Prep time: 10 min
Cook time: 35 min
Total time: 45 min
Cuisine: American
Ingredients: 2 bunches watercress (approx 12 oz); 3 tablespoons bacon grease, lard or other solid fat; 1 large onion, sliced; 2 stalks celery, sliced; 1 med-large rutabaga (1 lb), peeled and chopped; 3 cups chicken broth; 2 cups water; Generous pinch sea salt; Slices of ham or other protein (to serve; see text above); Watercress sprigs (to serve)