Cut the chicken in 6 pieces : 2 filet, each leg cut in half with skin and reserve in the fridge.
Add to a large stock pot 3 liters of filtered water, season the water with salt. Add the chicken carcass, onion, celery, 1 leek and the dark leaves from the leeks, 1 carrot chopped in chunks, bouquet garni. Let simmer for 2 hours. Sieve the broth, discard of the carcass and boiled veg, they gave their best!
Add the 6 chicken cuts to the warm chicken stock, simmer for 20 minutes on medium heat so the chicken is cooked through. Remove the chicken, remove the skin and reserve the chicken. Reserve the chicken stock.
Let the chicken stock boil to reduce. Boil the potatoes till cooked, sieve and reserve.
Slice the carrots in thin rounds. Cut the leeks in fine julienne. Add to a frying pan a table spoon of butter and toss the veg into the pan, saute them for a few minutes on low heat.
Half the chicken stock , freeze half to make soup later. Add to half the stock 2/3 of the cream, stir to combine . Make a "liaison": add in a bowl the left over cream and the 2 egg yolks and whisk them with a fork. Add the liaison to the chicken broth and stir over medium heat. Taste and adjust the seasoning with salt, pepper and nutmeg.
Add the chicken and veg, heat and ladle the waterzooi in deep soup dishes, sprinkle with the chopped parsley and serve with the boiled potatoes.