For the poached chicken stock: Place the chicken, carrots, celery, onion, garlic, lemon, herb bundle, peppercorns and salt in a pot, cover with water and bring to a low boil. Reduce heat to simmer and simmer for 1 hour minimum. Cool the chicken in the broth. Remove the chicken and cool. Separate the meat and pull or chop into bite-size pieces. Reserve for Broccoli Casserole
preparation. The chicken can be stored in plastic bag in the fridge for 4 days. Strain the stock and reserve for soup.
For the soup: Heat a soup pot over medium heat. Melt the butter and when it begins to foam, add the celery, onions and garlic; season with celery salt and pepper. Add the fresh bay leaf to the pot, partially cover, and cook until very tender and soft, about 20 minutes, stirring occasionally.
Add the potatoes, celeriac and stock and bring to a boil. Reduce heat to a low rolling boil and simmer, partially covered, for another 20 minutes, then puree with an immersion blender. Cool the soup and store for a make-ahead meal.
Place the soup in a stockpot and stir in the cream. Bring to simmer and taste to adjust seasoning. Serve in shallow bowls with Deviled-Ham Toasts alongside.