Spicy Peanut Stew

Name: Spicy Peanut Stew
Ingredients: 2 Tbs. olive oil; 1 medium onion, diced (about 1 cup); 1 celery stalk, chopped (about 1/2 cup); 1 Tbs. grated fresh ginger; 2 cloves garlic, minced (about 2 tsp.); 1 medium sweet potato, peeled and cut into 1-inch chunks (about 2 cups); 1 14.5-oz. can diced tomatoes with chiles; 1 lb. butternut or acorn squash, cut into 1-inch chunks (about 3 cups); 1/2 lb. cauliflower florets (about 4 cups); 1/4 cup creamy peanut butter; 6 cups cooked brown rice; 1 head watercress, stems removed