How to Make It
Bring a saucepan of water to a boil. Add the fava beans and blanch for 30 seconds. Drain and let cool under running water. Slip off the tough outer skins and transfer the beans to a bowl; you should have about 2 cups.
In the same saucepan, melt 2 tablespoons of the butter. Add half each of the fava beans and cauliflower and cook over moderately low heat, stirring, until the cauliflower is crisp-tender, 5 minutes. Add 1/2 cup of water, cover and simmer until the vegetables are tender, 5 minutes. Transfer to a food processor and puree until smooth, adding more water by the tablespoonful, if necessary.
Wipe out the saucepan and melt 2 tablespoons of the butter in it. Add the shallot, garlic and bay leaf and cook over moderate heat, stirring, until softened, 5 minutes. Add the rice and cook, stirring, until coated, 1 minute. Add the wine and cook, stirring, until it is absorbed. Add 1 cup of the warm broth and cook, stirring, until nearly absorbed; continue adding it 1 cup at a time, stirring until nearly absorbed between additions, until the rice is al dente, 20 minutes total. Halfway through cooking, stir in the remaining cauliflower.
Stir the fava-cauliflower puree into the risotto with the lemon juice, 1/2 cup of grated cheese and the remaining fava beans and 1 tablespoon of butter. Season with salt and pepper. Transfer the risotto to bowls and drizzle with oil. Serve with more cheese.