Preheat oven to 350 degrees F.
Combine, garlic, butter, parsley, salt and pepper in a bowl and stir to combine. Smear the insides of the slices with garlic butter and toast the whole loaf in the oven for 10 minutes until crispy and fragrant. Reserve left over garlic butter to top the cioppino with.
Place the chorizo 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 to cook until well colored and fat is rendered. Meanwhile add the garlic, celery, onion and drained tomatoes to the food processor and process until you have a smooth consistency of small vegetable pieces.
Once the ground chorizo is cooked, pour a two-count of extra-virgin olive oil and add the vegetable puree, thyme and bay leaf and saute for a further 5 to 7 minutes. When the liquid has cooked off a little, dust with the flour and stir well - this forms the base of a roux. Add the red wine, reserved tomato juice, and chicken stock. Season lightly with salt and pepper and then cover and simmer for 1 hour.
After 1 hour, turn the heat up and add the crabs and clams to the broth and steam until open, about 10 minutes. Reduce the heat and add the shrimp and fish fillets, gently mix to coat everything. Simmer gently until shrimp and fish are cooked then shut off the heat.
Serve cioppino with sourdough toasts and top with a spoonful of reserved garlic butter, some fresh parsley and the lemon.