Step 1Combine the egg, club soda and flour and whisk just until incorporated (do not over-mix). Season with salt to taste. Store the tempura batter in the refrigerator until cold and ready to use.
Step 1Combine the pepper, chiles, sugar, white vinegar, garlic and fish sauce in a blender until minced but not pureed. Add the honey and lime juice. Mix well. Add the pineapple, ginger, elderflower syrup, red wine vinegar and salt. Puree until smooth. Strain through a fine sieve, pressing on the ingredients with the back of a spoon, into a saucepan. Simmer over medium heat until reduced to about 2 cups, about 25 minutes. Keep warm.
Step 1Heat the oven to 425 degrees. Heat 1/2 cup of oil in a 10-inch skillet to 350 degrees. Season the filets with fleur de sel and white pepper to taste. Dip one side of each filet in the tempura batter. Working in 2 batches, fry the fish tempura-side down until golden brown, 2 minutes. Remove to a baking sheet and place tempura-side up. Fry the second batch, adding more oil if needed, and place on the baking sheet. Bake until the center of the fish is opaque, about 3 minutes.
Step 2To serve, sprinkle the pine nuts and ginger on each of 6 plates. Set the filets on top, then ladle the sauce around the fish and sprinkle with green tea powder.