Prepare all ingredients:
Shell the raw langoustines keeping the tails.
Place them to marinade in a little olive oil with pepper and a few sprigs of tarragon.
Meanwhile, chop the rest of the tarragon...
...and place in a small saucepan with the white wine.
Boil for 3 minutes.
Add the crème, bring to a boil...
...and combine with the egg yolks.
Baste with the juice of a lemon and keep hot without boiling. Whisk occasionally.
Mince the mushrooms and sautée them in olive oil.
When serving, heat the marinated olive oil on very high heat in a frying pan, throw in the langoustines and sizzle 2 minutes each side.
Remove them and make brochettes...
...by sticking mushrooms and langoustines alternatively.
Place in a warm dish,...
...cover each brochette with a slice of smoked salmon and coat with the tarragon sauce.