In a heavy bottom skillet sweat the onions with 10 gr of butter, add the rice and let it toast for 3 to 4 minutes (make sure no color) add the saffron and deglaze with white wine.
When the wine as evaporated add the hot stock or water little at the time keep stirring.
Continuing stirring the rice by adding liquid when start drying out.
When the rice is cooked remove from the stove and begin the mantecatura. (emulsify)
Mantecatura consist in adding the parmigiano and remaining butter in order to create a proper creaminess on the risotto.