Lentils add an interesting textural note to this hearty dish -- and combined with Arborio rice, they form a complete protein.
In a medium saucepan, combine 6 cups water, bay leaf, and thyme sprigs, and bring to a boil. Simmer for 5 minutes. Add lentils, reduce heat to low, and simmer until tender, 15 to 20 minutes. Drain lentils, discard bay leaf and thyme sprigs, and set aside.
Meanwhile, wash Swiss chard, and remove the leaves from the stalks. Slice the leaves into very thin 2-inch strips, and cut the smaller stems into 1/4-inch dice. Discard the larger stems. Cook Swiss chard in a wok or a large skillet over high heat, tossing constantly, until just wilted, about 3 minutes. Set aside in a colander.
Cut leeks in half lengthwise, and slice into very thin semicircles. Place in a large bowl of cold water, and let sit for about 5 to 10 minutes to rid them of dirt and sand. Lift out of the water, and drain in a colander. Set aside.
In a medium saucepan, bring stock to a boil, reduce heat to low, and keep at a bare simmer.
Heat olive oil in a heavy 4-quart saucepan over medium heat; add leeks, onions, and garlic, and cook, stirring frequently with a wooden spoon, until soft but not browned, about 6 minutes. Add rice and thyme leaves, and continue stirring until the edges of the rice are translucent, about 3 minutes. Add wine and cook, stirring constantly, until nearly all the wine is absorbed, about 30 seconds.
Raise the heat to medium high, add salt and pepper and about 1/2 cup of the simmering stock, and cook, stirring constantly, until nearly all the stock is absorbed. Continue adding stock, about 1/2 cup at a time. Cook, stirring constantly, allowing each addition to be nearly absorbed before adding the next, until rice is creamy but still a little firm in the center, about 15 to 20 minutes.
Remove the pan from the heat, and stir in lentils, Swiss chard, and Parmesan. Adjust the seasoning with salt and pepper, if necessary. Divide the risotto among six plates, and garnish with the shredded radicchio. Serve immediately.