Season chicken with seasoned salt and black pepper. Set aside.
Add the olive oil to a large skillet over medium-high heat. Place the chicken in the hot skillet and sear for 2-3 minutes per side, until golden brown.
Whisk together mustard, garlic, brown sugar, Worcestershire sauce, and apple cider vinegar until well blended. Reserve ¼ cup of the mixture.
Place the seared chicken in a baking dish or on a broiler pan.
Brush the tops of the chicken with the mustard sauce, then flip and brush the bottoms.
Bake for 10 minutes, then re-apply the mustard sauce to both sides of the chicken.
Bake another 10 minutes or until no longer pink in the center with an internal temperature of 165°F.
Serve with additional, warmed mustard sauce, if desired.