Heat a cast-iron pot and add the olive oil.
Peel the onions, cut them in half, and place them cut side down in the pot to color nicely.
Add the garlic, chili pepper, and chopped carrots and let them color nicely as well.
Add the shells, thyme, bay leaf, tomatoes, wine, and fish stock. Season with pepper and salt. Mix everything well and let it simmer for 25 minutes.
Strain the soup and press well in the sieve to extract every drop of juice.
Let the butter foam in a stew pot and stir in the flour all at once. Let it cook for a few minutes to avoid the flour taste.
Add half of the strained stock and whisk everything together until there are no lumps left. Then add the rest of the stock. If you still have lumps, use an immersion blender.
Remove the intestinal tract from the raw gambas and chop them finely.
Lightly whip the sour cream with a mixer and mix in the finely chopped gambas and spring onions.
Divide the bisque into deep plates and finish with quenelles of gambas tartare, some crayfish, and finely chopped spring onions. Drizzle some oil over the top as a final touch.
Tips
Before you add the carcasses, you can also extinguish with a shot glass of cognac or Armagnac. The crayfish can be replaced by hand -peeled shrimp. Also try to make the bisque with the waste from hand -peeled North Sea shrimp.