Put the saffron in a little bowl and fill it with boiling water (about ¼ cup, 60ml). Let it steep for about 30 minutes.
Finely chop the onion and add it to a pan drizzled with olive oil. Sautè at medium heat a couple of minutes, then add the rice and toast for 2-3 minutes.
Pour the wine and let the alcohol evaporate for a minute, then add enough stock to barely cover the rice and bring to simmer, then turn the heat to low.
Let it simmer for about 10 minutes, stirring it with a wooden spoon occasionally and adding more stock when it gets absorbed.
Add the saffron water to the rice and keep cooking the rice for about 10 more minutes, until the rice is al dente.
At the end of cooking the rice should still have some liquid but not too much. If it’s too dry add a bit more stock or water, if it’s too soupy, turn the heat to high for the last 5 minutes to evaporate more liquid.
Turn off the heat and add the butter and the grated Parmigiano cheese. Stir well until it’s all incorporated. Serve the creamy risotto immediately.
You can store leftovers in an airtight container in the fridge for about 2-3 days. Before reheating, add a couple of tablespoons of water to make it creamy again.