Preheat oven to 400ºF. Line a baking sheet with aluminum foil, and place a lightly greased wire rack on the baking sheet.
Place chicken between 2 sheets of heavy-duty plastic wrap; pound each cutlet to 1⁄4-inch thickness using the flat side of a meat mallet or small heavy skillet. Place flour and 1⁄2 teaspoon of the salt in a large ziplock plastic freezer bag. Combine egg, water, and 1⁄2 teaspoon of the salt in a shallow dish. Place panko in a separate shallow dish. Place 1 cutlet in bag; seal bag, and shake to coat with flour mixture. Dip floured cutlet in egg mixture; dredge in panko, pressing gently to coat cutlet completely, and place on wire rack. Repeat procedure with remaining cutlets. Coat cutlets with cooking spray. Bake in preheated oven until cutlets are golden brown and cooked through, 20 to 25 minutes.
Meanwhile, place shallots, capers, lemon juice, Dijon mustard, honey, and remaining 1⁄4 teaspoon salt in a mini food processor or blender; pulse until blended, about 5 times. With processor running, slowly pour canola oil and olive oil through food chute, and process until well blended. Combine Belgian endive, spring mix, and radishes in a medium bowl; toss with 3 tablespoons of the vinaigrette. Divide cutlets and salad evenly among 4 serving plates. Drizzle salads with remaining vinaigrette, if desired, and serve immediately.
Lemon pepperflavored panko makes the crispy breading extra tasty, but plain panko works well too.