For the beef tongue
Make a brine by boiling a big quantity of water with the sugar, the nitrite salt until these two elements are dissolved, then add the spices and let it cool. Put the tongue in the brine, cover with a plastic wrap and put aside in the fridge for 48 hours.
48 hours later, dry the tongue throughfully with a towel and put it 2 hours in a smokehouse with beech wood.
Once the tongue is smoked, put it in an aromatic broth (with onion, leek, carrot) and let it simmer for 4 to 5 hours. Let it cool in the broth. Peel it to obtain a beautiful piece of meat.
For the sauce
Mix the tarragon with a little water and filter with a thin sieve.
Mix the juice of tarragon with 1 tablespoon of cream, 1 tablespoon of ribot milk, 1 tablespoon of honey and a little salt, then emulsify with an arm mixer.
Cut the onion in thin stripes. Put the oignon in boiling water for 30 seconds and cool them in cold water. Place them a mix of 1/3 of vinegar, 2/3 of water and 2/3 sugar and 1/3 of salt. Count a minimum of 3 hours in the vinegar.
Cut the bread in two lenghtwise and hollow out it of a little its breadcrumbs, make it toast a few seconds on the barbecue.
Spread a spoon of sauce in the bread, then add 4 thin slices of pastrami. Add a spoon of trout eggs, a few leaves of tarragon and small stripes of onions pickles.