Trim the leeks to about two-thirds length, keeping the white parts and the tender green tops. Clean thoroughly under running water.
Place in a large pot, cover with water, and add coarse salt. Simmer for 1 hour. Drain in a colander for at least 30 minutes. Meanwhile, reduce the leek cooking liquid over medium heat.
Blanch spinach leaves in boiling water for 7 minutes, then drain and pat dry. Slice the salmon into very thin pieces.
Soften gelatin sheets in a bowl with cold water.
Pour the hot reduced leek stock over the gelatin and whisk vigorously until dissolved. Season lightly with salt and pepper—taste first, as the stock is flavorful.
Allow to cool completely.
To assemble: Line a pâté terrine mold with spinach leaves. Layer leeks at the bottom, seasoning with salt and pepper. Build layers about 2 cm thick, adding a thin layer of leek-gelatin mixture. Layer seasoned thin salmon slices over the leeks. Repeat until the mold is full. Fold over the spinach leaves.
Refrigerate for 12 hours.
Unmold and slice with a hot-water-dipped knife for clean cuts. Serve with pickles and a zesty lemon vinaigrette made with sherry vinegar and olive oil.
A signature creation by Chef Hubert.
