Rub chicken pieces with softened butter.

Broil chicken for 20 minutes, turning frequently, until lightly browned.

Place broiled chicken and giblets in a kettle.

Add leeks, celery, carrots, onions (with cloves), parsley sprigs, thyme, nutmeg, peppercorns, bay leaf, chicken stock, and white wine to the kettle.

Bring to a boil, then cover and simmer for 1 hour, or until chicken is tender.

Remove chicken and giblets from broth and cool.

Discard any cheesecloth or aluminum foil packet used for spices.

Strain the broth and skim off the fat.

Return broth to kettle and stir in lemon juice.

Cut the cooled chicken into big chunks and mince the giblets.

Remove bones and skin from the chicken.

Bring the broth to a simmer, then return chicken and giblets to the broth.

Heat through, covered, for 5 minutes.

In a separate bowl, beat egg yolks and heavy cream together.

Gradually whisk in a cup of simmering broth into the egg cream mixture.

Pour the egg cream mixture back into the kettle.

Rewarm at very low heat for a couple of minutes, being careful not to boil.

Ladle soup into deep bowls.

Garnish each serving with a thin lemon slice and minced parsley.

Serve hot.