Trim the  broccoli florets from the stems, keeping them small enough to fit on a spoon (you should have about 1 ¼ cups). Peel the stems with a small knife or vegetable peeler, then cut them into 2-inch pieces, steam the florets just until bright green, about 1 minute. Steam the stems until very tender, about 4 minutes. Reserve the steaming liquid.

 Transfer the stems to a blender or food processor, and process until smooth. You will probably have to add some of the steaming liquid to make a smooth mixture. Scrape out the puree into a small bowl, and set the florets and puree aside.

 If using the baby lima beans, cook them in a small saucepan of boiling salted water for 2 minutes, drain them thoroughly and set aside.

 Heat the olive oil in a heavy casserole or pot over medium heat, add the scallions and shallot and sauté until translucent, stirring often, about 4 minutes. Add the rice, and stir to coat with the oil. Toast the rice until the edges become translucent. 1 to 2 minutes. Pour in the wine, and stir well until evaporated. Add ½  cup of the hot stock and the ½ teaspoon salt. Cook, stirring constantly, until all of the stock has been absorbed.

 Continue to add hot stock in small batches—just enough to completely moisten the rice—and cook until each successive batch has been absorbed. After the risotto has cooked for 12 minutes, stir in the broccoli purée and the favas or limas. About 3 minutes after that, stir in the broccoli florets. Stir constantly, and adjust the level of heat so the rice is simmering very gently while adding the stock, until the rice mixture is creamy but al dente. This will take about 18 minutes from the first addition of stock.

 Remove the casserole from the heat. Whip in the butter first, until melted, then the grated cheese. Adjust the seasoning with salt, if necessary, and pepper. Serve immediately, ladled into warm shallow bowls.