Truss the chicken, submerge in cold chicken stock and slowly increase temperature to 80°C. Maintain this poaching temperature according to the weight of the chicken. Allow 1 hour of cooking time per kilogram, and add 10 minutes of cooking time per 100 g.
Refrigerate while still in the broth.
Place chicken on a rack, set aside broth for the sauce.
Crush the shellfish meat using scissors.
Sweat the garlic and shallots (unpeeled) in 100 g of butter along with the tomato paste.
Add the shellfish meat and sauté lightly, then add thyme and 500 g of butter.
Let simmer lightly for about thirty minutes.
Add pepper, let infuse for 5 minutes, then pass through a fine strainer. Allow the fat to settle. Remove fat, set aside.
Poultry shellfish sauce
Brown the shellfish heads, add shallots and cook 5 minutes.
Add garlic, tomato paste, and quartered tomatoes.
Add chicken stock and reduce by half.
Add cream and bring to the boil for several minutes.
Blend and pass through a filter cloth, season to taste and blend, adding shellfish butter.
Boil each of the vegetables separately; drain. Keep chilled. Brown shrimp lightly.