How to Make It
Place the oven rack in the middle position and preheat the oven to 350°.
In a small bowl, combine the sesame seeds, poppy seeds, shallots or onion powder, garlic powder and salt. You have just made your own Everything Bagel mix. Mazel tov!
Cut each pita into 8 even wedges. Tear or cut each wedge into 2 halves (each pita will yield 16 chips). Arrange the pita pieces in a single layer on a large baking sheet and brush with oil (use two baking sheets if necessary). Sprinkle each wedge liberally with Everything Bagel mix. Turn the wedges over and repeat the process with the oil and spice mix. Bake the pita until lightly golden and crisp, 7 to 10 minutes. Transfer the chips to a wire rack or plate and let cool.
Meanwhile, in a small bowl, fold the capers into the sour cream.
On a large platter, spread half the pita chips in a single layer, top with half of the sour cream mixture, whitefish, onion, cucumber and tomato. Repeat with the remaining chips, sour cream, fish and vegetables. Sprinkle with dill and serve immediately.