Peel and chop carrots into medium-sized pieces.

Combine carrots and chicken stock in a pot.

Bring to a boil, then reduce heat and add salt, pepper, sugar, and cinnamon.

Simmer, covered, until carrots are very tender.

Puree the soup using a food processor or blender until smooth and creamy.

Melt butter in a separate saucepan.

Add flour and cook over low heat for a few minutes, stirring constantly to create a roux.

Gradually whisk in hot milk until the mixture thickens into a smooth sauce.

Remove from heat.

Just before serving, whisk egg yolks one at a time into the butter, flour, and milk mixture.

Gradually add the egg yolk mixture to the pureed carrot soup, stirring vigorously.

Heat through, stirring constantly, until the soup thickens slightly, but do not boil.

Remove from heat immediately to prevent curdling and serve hot.