Heat the olive oil in a soup pot over medium heat. Add the leeks and saute until just beginning to wilt, about 1 minute. Add 1/4 cup of water, cover and simmer 10 to 15 minutes or until tender and wilted.
Add the tomatoes, beans, rice and broth and water.
Bring the liquid to a boil; season to taste with salt and pepper. Cover the pot and cook gently over low heat until the rice is tender, about 20 minutes.
Meanwhile stem the spinach and mustard greens, rinse them well and chop coarsely.
Add them to the pot and simmer 3 to 4 minutes just until tender. Adjust the seasoning and serve very hot as is or float cheese crusts on top if you wish.
Cheese crusts: slice some lovely good bread on the bias, toast lightly, then top with grated Parmesan or other cheese of choice and melt in toaster oven or broiler.