Steep the saffron threads in 4-5 tablespoons of hot water in order to release all of their aromatic properties for at least 10 minutes. Longer is better;
Bring the stock to a boil. Keeping the stock hot helps to coax the starch gently out of the grains of rice. Adding cold stock will keep the risotto from becoming creamy;
In a heavy pan or stockpot, heat 2 tablespoons (40g) of butter over high heat and add the thinly sliced onion;
Stir until softened (about 2 mins);
When the onion is tender and translucent, lower to medium heat and pour in the rice stirring to thoroughly coat until they become toasted and translucent for about 2 minutes;
Add the white wine and stir until it evaporates;
Add the stock, 1/2 cup at a time, stirring constantly until it is nearly absorbed in between additions;
Add the water with the saffron;
After all the stock is added and you can see the bottom of the pot when you stir, remove it from the heat and stir in the remaining butter and the cheese;
Serve it on a cold plate.