Bring stock to a simmer in a saucepan; add the saffron and leave to infuse.
Melt the butter in a large saucepan over medium heat and sweat the onion and celery until softened but not colored.
Add the rice stir until it's coated with the oil.
Add the stock and bring to a boil. Salt and pepper to taste.
Reduce the heat, stir and leave to cook covered for 15 - 20 minutes until the rice is Al dente and the liquid is absorbed.
Fluff the rice.
Stir in the chicken and parsley and allow it to warm through the heat of the rice.
* This recipe calls for parboiled or converted rice. In the US, look for Uncle Bens Converted Rice, or Golden Canilla Parboiled Rice. In the UK, buy Uncle Bens Long Grain Rice (not quick cook).Substituting The RiceYou can use other types of long-grain rice (although I don't recommend instant, quick-cook, or brown rice). Just be sure to consult the package instructions for the rice to liquid ratios and cooking times and adjust accordingly.