Make the sauce: Mix the onion, both mustards, the mayonnaise, paprika, garlic powder and salt to taste in a bowl. Set the sauce aside.
Make the chips: Heat 1/2 inch vegetable oil in a large skillet over medium heat. Gently pat the pickle slices dry with a paper towel.
Put the pretzels in a large resealable plastic bag and crush into coarse crumbs using a rolling pin or heavy pan; transfer to a plate. Whisk the eggs in a shallow bowl and put the flour in another bowl. Dredge the pickle slices in the flour, shaking off any excess; dip in the beaten eggs, then dip in the pretzel crumbs, turning to coat. Working in batches, fry the pickles until golden and crisp, about 1 minute per side. Drain on paper towels and sprinkle with celery salt, if desired. Serve warm with the mustard sauce.
Photograph by Yunhee Kim
Recipe courtesy of Danica Preston for Food Network Magazine