4 cups apple cider
1 tablespoon light brown sugar
1 tablespoon kosher salt, plus more
6 chicken cutlets, pounded to ⅛” thickness
6 ounces pretzels
4 large eggs, beaten to blend
⅓ cup whole grain mustard
¾ cup all-purpose flour
Freshly ground black pepper
Vegetable oil (for frying; about 3 cups)
Flat-leaf parsley leaves with tender stems and lemon wedges (for serving)
Bring apple cider, brown sugar, and 1 tablespoon kosher salt to a boil in a medium saucepan and cook until reduced by half, 10–15 minutes. Transfer to a shallow dish and let cool. Add chicken, cover, and chill at least 6 hours.
Pulse pretzels in a food processor to coarse crumbs; transfer to a shallow bowl.
Whisk eggs, mustard, and 2 tablespoons water in another shallow bowl. Place flour in a third shallow bowl. Remove chicken from brine, pat dry, and season with kosher salt and pepper. Working one at a time, dredge in flour, shaking off excess. Dip into egg mixture, letting excess drip back into bowl, then coat with pretzel crumbs, pressing firmly to adhere.
Meanwhile, pour oil into a large skillet to a depth of ½” and heat over medium-high heat until it bubbles immediately when a pinch of flour is added.
Working in batches, fry chicken until golden brown and cooked through, about 2 minutes per side. Drain on paper towels; season with kosher salt. Serve schnitzel topped with parsley, with lemon wedges for squeezing over.