Put your saffron threads into a small glass. Add warm water over the saffron so it is completely covered, gently mix and leave to infuse overnight, in this way they will release all their colour.
Prepare the vegetable broth using aromatic herbs to flavour it: a few bay leaves and savory is delicious, you need a a litre
Add a spoonful of the saffron infusion to the broth.
Peel and finely chop the onion so that it can melt while cooking and not be perceived when you finally savor the delicious risotto.
In a large saucepan add 50g of the butter, melt it over low heat, then add the chopped onion and let it simmer for 10-15 minutes adding broth to keep the sauce from drying out: the onion should be very transparent and soft.
Once the onion is stewed, pour in the rice and toast it for 3-4 minutes, to seal the grains of rice and ensure an even cooking.
Add the Prosecco and let it evaporate completely. After which cook the rice for between 18-20 minutes, adding the broth a ladle at a time, as needed and as it is absorbed by the rice: the grains must always be covered.
Five minutes before the end of cooking, pour the remainder of your saffron infusion and the stigmas to flavour and dye the risotto a beautiful gold colour.
After cooking, turn off the heat, stir in the grated cheese, the remainder of the butter, mix and cover the pan with a tea towel for 2 minutes to infuse.
Serve hot, garnishing the dish with some saffron threads and, if you like, a few flat-leaf parsley leaves.