Tunisian Soup

Ingredients : 2 tablespoons butter 1 onion chopped 1 cup couscous 8 cups water 2 zucchini chopped 1 potato chopped 20 green beans chopped 2 carrots chopped 2 tablespoons tomato puree ½ teaspoon ground coriander ½ teaspoon red chile powder ½ teaspoon ground cumin ¼ teaspoon salt ½ cup milk...