Heat up fish stock to a simmer, allow to cool for 3 minutes, dissolve in gelatin sheet. Cut escolar into 2 broad thin sheets, measuring approximately ½” thick X 2” wide X 6” long. Cut tuna into 1 broad thin sheet, measuring approximately ½” thick X 2” wide X 6” long. ‘Paint’ one side of each piece of escolar with the jellied fish stock. ‘Paint’ both sides of the tuna piece. Assemble ‘sandwich’ by ‘sandwiching’ the tuna piece between the two escolar pieces. Making sure that the ‘painted’ sides of the escolar are touching the tuna and the ‘unpainted’ side of the escolar is the outside of the ‘sandwich’. Wrap the sandwich tightly in plastic wrap and refrigerate for a minimum of 4 hours.
Blanch and shock green onions in boiling water and ice bath, respectively. Mix all ingredients in a blender except the mayonnaise. Puree completely. Fold puree into mayo and taste for seasoning. Additional ingredients: Louisiana Caviar, lemon juice marinated red onions. Season each sandwich with salt and sear in a very hot pan with a little canola oil on each side till escolar is nicely brown. Remove to paper towels to drain excess oil. Slice ‘sandwich’ into 1” cross-cuts. Place 1 oz of green onion emulsion on a plate, arrange 4 slices of sandwich on top and garnish with Louisiana caviar and lemon juice marinated red onions.