Step 1: Prep Chicken. Pat the chicken breasts dry with a paper towel, then carefully slice each in half horizontally to form two thin cutlets. Using a meat mallet or a rolling pin, pound each piece until no more than ⅓-inch thick. Season the chicken evenly with ~3/4 tsp. kosher salt and 1/2 tsp. black pepper.
Step 2: Chop or Blitz Pecans. Finely chop the pecans by hand, pulse in a food processor, or place in a gallon-size zip-top bag and crush with a rolling pin. Aim for small, evenly-sized pieces that resemble coarse crumbs, being careful not to crush them into a fine powder.Step 3: Setup Dredging Stations. Place the flour in a shallow bowl or rimmed plate. Crack the eggs into a second bowl and whisk them with a fork. In a third bowl, combine the pecan crumbs, Panko, paprika, onion powder, garlic powder, and 1/2 tsp. kosher salt. Step 4: Mix Dijon Dressing. Combine vinegar, maple syrup, and mustards in a small mixing bowl; mix well. Gradually stream in olive oil, whisking constantly, until emulsified. Season to taste with salt and pepper, and set aside.
Step 5: Bread Chicken. Working one at a time, dip the chicken breasts into the flour, shaking off any excess, then into the egg mixture, then the pecan-panko mixture, pressing to adhere. Place the chicken breasts on a baking sheet until ready to cook.
Step 6: Prepare Apple-Celery Salad. In a large mixing bowl, combine shaved apple, celery, cheese, parsley, and dates. Add half of the Dijon Dressing and toss to combine. Season to taste with kosher salt and black pepper.
Step 7: Cook Chicken. Heat ~1/4 cup olive oil or avocado oil in a large (12-inch) skillet over medium-high. When the oil is hot (it should sizzle immediately if you drop a bread crumb into the pan), carefully place 2 to 3 cutlets in the pan. Lower the heat to medium and cook about 3 minutes per side, until golden-brown and cooked through.Transfer to a wire rack and sprinkle with flaky salt, if desired. Repeat with the remaining cutlets, adjusting the heat as necessary. *Pecans contain natural oils and can brown quickly, so keep the skillet over medium heat to avoid burning. The chicken should reach an internal temperature of 165ºF. Serve each chicken cutlet topped with apple-celery salad and a drizzle of remaining Dijon dressing.