Sauce nantua

1. Make a mirepoix of the onion, carrot, shallots, thyme, bay leaf, parsley, salt and pepper.
2. Sautei the mirepoix in ¼ cup of olive oil until tender.
3. add crawfish heads and garlic, cooking until the heads are red. add white wine, brandy, fish stock and tomato puree and simmer for 15 minutes, then strain, reserving the heads.
4. when the heads are dry, grind them in a grinder or food processor.
5. Add the ground heads to the liquid and simmer again for 10 minutes.
6. strain very well and discard the heads.
7. make a roux from the butter and flour and add to the liquid to make a liaison.
8. Finish the sauce with cream, brandy, salt, pepper and cayenne.
9. Ladle over mousseline and garnish with crawfish tails.