For the halibut, divide it into four equal portions. Season the fillets with salt, pepper and lemon juice. Sear halibut on both sides and finish in the oven at 180°C.
For the shellfish sauce, rinse the carcasses well under cold water and drain. Heat the clarified butter in a pot. Add the carcasses and diced vegetables and sauté. Deglaze with the cognac and flambé.
Add the white wine. Puree the tomatoes in a blender and stir them in. Mix in all the spices and herbs and pour in cold water. Let it simmer for 20 minutes at low heat. Line a sieve with a straining cloth and strain the stock. For the saffron pumpkin cream, butter the inside of a casserole. Add the pumpkin and saffron and cook in the oven at 180°C for 30 minutes until soft. Mix in a blender with cold butter, olive oil and honey. Strain through a fine sieve and season to taste. Serving:Place pumpkin puree in the center of the plate with the help of a ring. Place halibut fillet on top and nap with crustacean stock. Garnish with the pumpkin cubes and brittle.