Heat 2 tablespoons extra virgin olive oil in a wide skillet over medium heat. Add 2 cloves garlic, sliced, and shake the pan until the garlic is lightly browned. Slide in 2 cups halved cherry tomatoes and stir gently until they are juicy. Toss in a handful of shredded fresh basil, remove the pan from the heat, and set aside.

Pour the stock into a 2 quart saucepan and keep it hot over low heat. (The texture of a properly cooked risotto is creamy, with each grain of rice separate and al dente. To achieve that, you are actually coaxing the starch gently out of the grains of rice. Adding cold stock to the risotto may cause the surfaces of the grains of rice to seize up and seal in the starch, instead of releasing it into the liquid.)

Heat the olive oil in a wide 3 to 4-quart braising pan over medium heat. Stir in the onion and cook, stirring occasionally, until softened, about 4 minutes. Stir in the leek and white parts of the scallions and cook, stirring, until the onion is golden, about 6 minutes. Adjust the heat under the pan as the onion browns so that it cooks slowly with gentle bubbling.

Stir in the rice and continue stirring until the grains are coated with oil and toasted, the edges become translucent , about 1 to 2 minutes. Pour in the wine and let it boil, stirring the rice, until evaporated. (Since the rice kernel is 98 percent starch, the acidity in the wine balances and imparts flavor to the rice kernel.)

Season the rice lightly with salt and ladle enough of the hot stick into the pan to barely cover the rice. Bring to a boil, then lower the heat so the stock is at a lively simmer. Cook, stirring constantly, until all the stock has been absorbed and you can see the bottom of the pan when you stir. Continue cooking, pouring in the remaining hot stock in small batches-each additional should be just enough to completely moisten the rice-and cook until each batch of stock had been absorbed. Stir constantly until the rice mixture is creamy but al dente, this will take 16 to 20 minutes from the time the wine was added. Stir in the sauteed cherry tomatoes halfway through cooking. When in doubt, undercook-risotto will continue to cook, even after it is removed from the heat.

Adjust the level of heat throughout cooking so the rice is simmering very gently. The total amount of stock you may use may vary for several reasons: the type of rice you are using, the shape, the size of the pan, and the desired texture of the finished risotto which can be quite dense, or soft and runny, depending on your personal taste. If you like a creamier risotto-called all’onda or wavelike in Italian- stir in a little more stock once the rice is al dente, but do not cook the rice any further. For a denser risotto, keep the rice over the heat and cook until the last addition of the stock has been almost entirely absorbed by the rice. There is a general rule that risotto with seafood is looser and risotto prepared with meats, game, and mushrooms is more dense, but ultimately it depends on your taste and preference.
Remove the pan from the heat; Stir in half the grated cheese, taste the risotto, and add salt, if necessary, and pepper. Stir in 1 ½ cups of cubed fresh mozzarella (preferably mozzarella di bufala) along with the grated cheese and butter. Stir in butter and green parts of the scallion until the butter is completely melted.

Always ladle risotto into warm, shallow bowls and serve immediately after finishing. Either top each serving with some of the remaining grated cheese or pass the cheese separately.