How to Make It
In a large saucepan, heat the oil until shimmering. Add 4 of the chestnuts and sauté over moderately high heat until lightly browned, about 5 minutes. Transfer to a plate and let cool. Add the onion and leek to the pan, cover and cook over moderate heat, stirring occasionally, until softened, about 5 minutes. Uncover and cook over moderately high heat, stirring frequently, until lightly browned, about 4 minutes. Add the honey and stir until melted. Stir in the remaining chestnuts and the stock, season with salt and pepper and simmer over moderate heat for 10 minutes.
Finely chop the sautéed chestnuts. Working in batches, puree the soup in a blender until smooth. Strain through a fine sieve. Season the soup with salt and pepper and stir in the Cognac. Ladle the soup into shallow bowls. Garnish with the chopped chestnuts and parsley and serve.