This vegetarian stew is just as satisfying as one made with beef.
Pick over beans, discarding any stones or broken beans, and rinse. Place in a large saucepan, cover with cold water by 2 inches, and bring to a strong boil. Remove from heat, and let stand 1 hour, covered. (Alternatively, beans can be placed in a bowl, covered with 2 inches of cold water, and soaked overnight.)
Drain beans, place them in the saucepan, and add enough cold water to cover by 2 inches. Tie peppercorns in a small piece of cheesecloth, and add to beans along with bay leaves and onion slices. Return the mixture to heat, bring to a boil, and reduce heat to medium low. Simmer until beans are very tender, 35 to 40 minutes, adding 1 teaspoon salt about 10 minutes before beans are finished cooking. Remove from heat, set aside, and let beans cool in their liquid. They can be cooked and refrigerated in their liquid up to 2 days in advance.
Meanwhile, fill a large bowl with cold water. Cut lemons in half, squeeze juice into water, and add lemon halves. Trim about 1/2 inch from tips of artichokes, and pull off tough outer leaves. Trim stems to 1/2 inch, and trim off dark green outer layer of stem. Slice artichokes in half lengthwise if small or in quarters if large. Use a small sharp knife to remove the purple choke from artichokes -- if the choke is not purple, it is not necessary to remove it. Place prepared artichokes in the bowl of lemon water. Set aside.
Remove basil leaves from stems, discard stems, and wash leaves thoroughly. Drain and lay leaves out on paper towels, blotting away as much water as possible. Place basil in the bowl of a food processor, add 4 tablespoons olive oil, and process until smooth, about 2 minutes. Transfer puree to a small bowl, cover immediately with plastic wrap to prevent discoloration, and refrigerate until needed.
Cut leeks into 1/2-inch rounds, and place in a large bowl of cold water. Let sit for 5 to 10 minutes to rid them of any dirt and sand. Lift out of the water, and drain in a colander.
Heat remaining 2 tablespoons olive oil in a Dutch oven or large saucepan over medium heat. Add leeks, garlic, 1 teaspoon salt, and 1/8 teaspoon pepper, and cook until fragrant and tender, stirring frequently, about 10 minutes. Drain artichokes, discarding the liquid and lemons, and add to leeks along with wine. Cover, and cook until artichokes begin to become tender, about 15 minutes. Uncover, and cook until liquid evaporates and artichokes are tender, about 5 minutes more.
Meanwhile, cut radicchio heads into 1-inch wedges without removing the core; it will hold the leaves together. Drain cooked beans, reserving cooking liquid. Remove and discard bay leaves, onion slices, and peppercorns. Add beans, 2 cups of the cooking liquid, remaining 1 teaspoon salt, and remaining 1/8 teaspoon pepper to leeks and artichokes. Cook until beans are heated through and liquid has thickened, about 15 minutes. Stir in radicchio wedges, and cook until wilted, about 5 minutes. Adjust seasoning with salt and pepper, if necessary. Stir in 3 tablespoons of the basil puree. Serve immediately with the remaining basil puree on the side.
This vegetarian stew can be made up to a day in advance and reheated -- just add the radicchio and the basil puree right before you reheat the stew.