Heat oil in a thick casserole or Dutch oven and fry the onions till slightly soft. Add the chicken pieces dusted with flour and quickly brown (not too much or the onions will burn).
Throw in the carrots and potatoes, cook for a couple of minutes and pour in the stock with the cinnamon stick, chilli flakes and salt. Bring to a boil, lower heat, cover and simmer till vegetables are tender but not mushy.
Remove the chicken, shred and discard the bones.
In a small bowl, beat the egg yolks with the lemon juice and mix in the herbs and the saffron soaked in water.
Add the vermicelli to the soup and cook for a further 7-8 minutes till they are done. Mix in the chicken followed by the egg mixture. It's important to keep the heat low or take the pan off the heat while stirring the eggs in. Once mixed, return to low heat, simmer for 2 minutes, add the pepper and serve piping hot.