A drizzle of tangy lemon-mustard sauce brightens chicken cutlets while mellowing crisp-tender wedges of quick-cooked radicchio.
Place flour in a shallow bowl; season with salt and pepper. Dredge chicken in flour, shaking off excess.
In a large skillet, heat 1 tablespoon oil over medium-high. Add half the cutlets; cook until lightly browned and cooked through, 1 to 3 minutes per side (reduce heat if browning too quickly). Transfer chicken to a plate, and cover with aluminum foil to keep warm. Cook remaining cutlets, and add to plate; cover and set aside (reserve skillet).
Wipe out skillet with a paper towel. Add remaining tablespoon oil, and place over high heat. Add radicchio, cut side down, and sear, without turning, until lightly charred, 1 to 2 minutes. Turn and repeat on other side. Serve chicken and radicchio drizzled with sauce.