In a small saucepan, boil the balsamic vinegar over moderately high heat until reduced to 2 tablespoons, about 10 minutes.
In a medium saucepan, bring the vegetable stock to a boil. Cover and keep hot.
In a large saucepan, heat the olive oil. Add the shallot and bay leaf and cook over moderate heat until the shallot is softened, about 3 minutes. Add the rice and cook, stirring, until the grains are evenly coated with oil, about 1 minute. Add the wine and simmer over moderate heat until it is almost evaporated, about 4 minutes. Add enough of the hot stock to just cover the rice and cook, stirring, until the stock has been absorbed. Continue adding the stock 1/2 cup at a time, and stirring constantly, until it is nearly absorbed between additions. The risotto is done when the rice is al dente and suspended in a thick, creamy sauce, about 25 minutes.
Discard the bay leaf and stir in 1 tablespoon of the balsamic reduction. Stir in the butter and the three tablespoons of cheese and season with salt and pepper. Spoon the risotto into bowls, drizzle with the remaining 1 tablespoon of balsamic reduction and sprinkle with more cheese. Serve right away.