For the brook trout in parchment with young garden vegetables, wash the ready-to-cook brook trout and pat dry. Peel asparagus and cut away woody parts. Cut celery (without green) into small cubes, yellow beets into slices and fennel bulb (without green) lengthwise. Blanch (scald) all vegetables briefly in salted water and rinse in ice water, drain.
Peel lemon with a zester, cut peel into fine strips and blanch briefly in salted water. Squeeze the lemon. Rub the fish with salt, coriander, pepper, juniper and lemon zest and juice. (To do this, pound all the spices and some salt with the lemon peel, preferably in a mortar).
Then glue baking or parchment paper together with egg white to make an area about 60 x 60 cm (or four smaller ones). Place on a baking sheet and moisten with water. Spread out vegetables on the parchment. Fill the belly of the fish with fennel and celery greens and place the fish on top of the vegetables. Drizzle Noilly Prat and lemon juice over the top and top with butter flakes. Close parchment tightly and brush the fold well with egg white.
Cook in preheated oven for about 30 minutes. Remove the brook trout in parchment with young garden vegetables, serve in the wrapper and open only at the table.