Chicken Vegetable Aspic
Rinse chicken and place in a large pot. Cover chicken with cold water and bring to a boil, skimming foam if necessary. Peel onion, carrot and celery root, chop coarsely and place in pot with chicken. Add bay leaves and juniper berries to pot and simmer about 2 1/2 hours over low heat. Add more water if necessary. Remove chicken from pot and let cool. Strain cooking liquid, remove fat and set vegetables aside. Boil about 500 ml (approximately 2 cups) broth and reduce heat to simmer.
Remove chicken meat from bones and cut into strips.
Soak gelatin sheets in a bowl of cold water until softened, about 10 minutes. Rinse and dry bell peppers, halve and remove seeds and ribs. Place halved bell peppers cut-side down on a roasting pan and place under preheated broiler. Roast bell peppers until skin blackens and begins to burst. Cover roasted peppers with a damp cloth and leave to cool. Peel skin from roasted bell peppers and cut flesh into small pieces. Rinse spinach leaves, removing stems if necessary.
Cool broth slightly and squeeze gelatin sheets. Stir gelatin sheets into broth and let dissolve. Stir white wine into broth and season with sherry, salt, sugar and pepper. Let cool until liquid slowly starts to set.
Mix chicken and vegetables into partially set gelatin. Line gelatin mold or baking dish with plastic wrap. Pour gelatin mixture into prepared mold. Add or remove liquid to cover solids and fill mold to the brim. Cover mold and refrigerate to set, overnight or at least 4 hours.
To serve, remove aspic from mold and cut into pieces. Serve with spinach and garnish with chervil.