In the saucepan, warm the stock to just below a simmer. There is no need to boil it but you want it hot.
The stock is hot, take about ¾ of a cup and put it in a small bowl. Sprinkle the saffron threads into the stock, stir and set aside.
In the large pan, add the olive oil and cook, over medium low, the leeks and shallots. You are looking to soften these without getting much, if any, color on them. Once the leeks and shallots are softened and cooked, add 2 tablespoons of butter and when it is melted, stir in the rice and turn the heat to medium. Make sure to stir well to completely coat the rice. Toast the rice for about 3 minutes.
Stir in the wine and cook for a few more minutes until the wine is nearly completely absorbed by the rice.
Start adding the hot stock to the rice a ladle (about ½ to ¾ of a cup) at a time. Stir often and wait until the rice has absorbed most of the stock before adding another ladle. You may need to turn the heat down and you want a simmer, not a violent boil.
After the first three additions of stock, the next addition will be the small bowl of stock with the saffron threads. Continue the same process until the rice is done. Start checking by tasting a little of the rice at about 18 minutes into cooking for doneness. As a guideline, risotto will take between 20-24 minutes to finish but taste the rice for a perfect al dente texture. Once the risotto is almost done, stir in the salt and pepper, then take off the heat.
Finish the dish by stirring in the remaining butter and the Parmigiano Reggiano. When you serve the risotto, you can sprinkle some fresh finely chopped parsley on top.