In a medium bowl, combine chopped capers, dill pickles, fresh dill, and sliced marinated green olives. Drizzle with extra virgin olive oil, stirring gently until everything is well-coated.

In a small mixing bowl, whisk together kewpie mayo, Dijon mustard, freshly chopped dill, lemon zest, lemon juice, minced garlic, onion powder, and a pinch of salt and pepper.

Thinly slice the fennel and celery before tossing them in a mixing bowl. Drizzle with a splash of olive oil and lemon juice, mixing gently until evenly coated.

Set up a breading station with three shallow bowls: one for all-purpose flour mixed with celery salt, another for the beaten egg, and a third for panko crumbs. Coat each fish strip in flour, dip it into the egg, and finally press it into the panko.

Heat a large skillet over medium-high heat and pour in enough olive oil to cover the bottom. Fry the breaded fish fingers for about 2-3 minutes on each side until golden brown.

Slice the green olive focaccia in half and spread a generous layer of the dill tartare sauce on both cut sides. Layer the crispy fish fingers evenly, followed by the crunchy fennel-celery slaw.