Wash the chicken breast fillets and pat dry. Wash tarragon, spin dry and chop finely. Rub the chicken breast fillets with pepper, sprinkle with tarragon, drizzle with lemon juice and marinate for at least 10 minutes.
Peel the shallots and cut into fine rings. Rinse the crabs and pat dry. Remove the meat from the marinade, dry it well and cut into 1 cm wide strips. Save the marinade.
Fry the meat strips in hot butter until light brown on all sides, add the shallots, fry for 1 minute, then add the crabs, also fry for 1 minute.
Add the crème fraiche and white wine and let it get hot. Season to taste with salt, cayenne pepper and the remaining marinade, add cream if necessary.