Place your chicken thighs into a large saucepan.
Add the carrots and green beans.
Pour hot water over these ingredients until your pan is around ¾ full.
Bring to the boil and then simmer on a medium heat for 10 minutes.
Now add your potato, salt, pepper and saffron to the pan.
Stir everything together, cover and leave to simmer for around 45 minutes.
In a bowl, add your egg yolks and the flour and mix together into a thick paste.
Stir in the water a little at a time until the paste is smooth.
Now squeeze in the lemon juice and mix.
Ladle a small amount of your soup stock into the bowl and stir that in slowly.
Now pour this mixture into your pan of soup a little at a time, stirring your soup as you do so.
Simmer your soup for a couple of minutes and then serve.
Feel free to squeeze in more lemon juice for extra tang.