Pour the stock or broth into a saucepan and warm on the stovetop. It doesn't need to boil or simmer, you just want it warm. The saltiness of the stock is what will season the risotto. If using a homemade vegetable broth or a stock that is perhaps on the bland side, we recommend salting it to taste.

Meanwhile, add the rice into a small saucepan or skillet and toast over medium heat for 2-3 minutes, stirring frequently to avoid burning. Turn off the heat and set aside.

In a skillet or shallow pot, add half the butter, the bone marrow (optional), and the diced onion. Sauté over medium/low heat for 2-3 minutes, or until the onion is tender and slightly translucent, then add the rice. Stir all together until the rice is completely coated in butter, then pour in the white wine.

Lower the heat and bring to simmer. Cook until the rice has absorbed almost all of the excess liquid. Use a ladle to spoon in just enough of the warm broth to submerge the rice. Bring the risotto to a gentle simmer.

The rest of the cooking process will involve simmering the rice, stirring occasionally, and adding a little more broth as needed to maintain the moisture in the pan. Usually it takes about 16-17 minutes for carnaroli rice to reach "al dente," but consult the recommended cook time for the particular rice you choose and trust your taste!

While the risotto cooks, mix the saffron with about a ¼ cup of the warm broth. Pour this into the risotto.

When the rice is about 2 minutes away from reaching al dente, stop adding stock so that the risotto has a chance to thicken. When you feel that the rice is cooked and the consistency is correct (soft and creamy but not soupy), turn off the heat. Stir in the remaining butter and Parmigiano cheese.

Cover the pan and allow the risotto to rest for 2-3 minutes before serving. Buon appetito!