Step 1Heat the oil in a large saucepot over medium heat. Add the onion, carrots and leeks, and cook until the vegetables are tender, about 5 minutes. Add the garlic and cook another 5 minutes.
Step 2Stir in the chicken and vegetable broths. Heat to boiling, then reduce the heat, cover, and simmer 30 minutes. Stir in the potatoes and continue to cook, covered, until the potatoes are tender, 20 minutes. Stir in the peas and simmer 5 minutes. Stir in the watercress. Serve topped with the croutons.