Place the chorizo, onion, garlic, celery, and tomatoes in a food processor and process until the pieces are small and well ground up. Heat a Dutch oven over medium heat and add the ground chorizo and vegetables to cook until well colored and fat is rendered. Once the ground chorizo and vegetables are cooked, add the flour, thyme and bay leaves. Saute for a further 5 to 7 minutes (this forms the base of a roux). Then add the red wine, reserved tomato juice, and chicken stock. Season lightly with salt and pepper and then cover and simmer for 30 minutes. With 10 minutes to go, turn the heat up and add the crabs and clams to the broth and steam until open, discarding any un-open ones. Reduce the heat and just prior to service add the shrimp and shut off the heat so they don't get over cooked. Remove and discard bay leaves.
While the cioppino is cooking, prepare the halibut. Season the fillets with salt and pepper and fresh thyme. Heat a large nonstick saute pan and add a 2-count of olive oil. Cook fillets 4 minutes on 1 side then turn once briefly before setting on paper towels to drain.
Preheat oven to 350 degrees F.
Combine, garlic, butter, parsley, salt and pepper in a bowl and stir to combine. Smear the inside of the bread with garlic butter and toast on a sheet tray in the oven. Reserve any left over garlic-butter to serve with the cioppino.
To serve, set garlic sourdough toasts in the bottom of a flat bowl. Top with halibut then ladle over cioppino. Top with a spoonful of reserved garlic butter. Garnish with fresh flat-leaf parsley and serve.