Make the soup: Bring stock to a gentle simmer in a medium saucepan. Add sugar snap peas and carrots, and simmer for 1 minute. Remove from heat, and season with 1 1/2 teaspoons salt and some pepper. Stir in chickpeas, watercress, and basil.
Make the toasts: Stir together cheeses and scallions. Spread onto toasts, and sprinkle with pepper. Serve soup with toasts.