Summer roll: Place all ingredients except rice paper in a bowl with the white vinegar and sugar. Reconstitute rice paper with the hot water. Fill paper with vegetables, crab and sausage. Roll up and slice into 2 pieces. Repeat with remaining rice papers.;
Sweet and sour sauce: Cut pineapple, put in blender and strain out the juice. Add the juice, vinegar, sugar and Sriracha to a small saucepan and bring to a boil. Combine the cornstarch and water and slowly add to the simmering sauce. When thickened, remove from the heat. Chill and pout into a squeeze bottle.
Scallion-Cilantro Puree: Put all ingredients for puree in blender, blend until smooth and pour into squeeze bottle.
Prawns: Split tails open on the prawns and remove antennas. Crush the Szechwan peppercorns and season prawns along with the salt. Add the oil to a large skillet over medium-high heat. Once heated add the prawns, remove the head and drizzle juices on tail.
Garnish: Plate mache, top with summer roll slightly off center and a prawn. Dust all with gold leaf and sauce the plate with scallion-cilantro puree. Dot plate with sweet and sour sauce and garnish prawn tails with edible orchid.