Prep the chicken: If using thick breasts, slice them in half horizontally to make cutlets. Pat dry with paper towels. Season both sides with salt, pepper, paprika, and garlic powder.
Heat the skillet: Set a large nonstick or stainless-steel skillet over medium-high heat.
Add 1 tablespoon olive oil and swirl to coat.
Sear the chicken: Add chicken in a single layer. Cook 3–4 minutes per side, until golden and the centers are just cooked through (internal temp should reach 165°F/74°C). Transfer to a plate and tent loosely with foil.
Sauté the garlic: Reduce heat to medium.
If the pan is dry, add another 1–2 teaspoons oil. Add minced garlic and cook 30–45 seconds until fragrant, stirring so it doesn’t brown.
Build the sauce: Add lemon zest, lemon juice, and chicken broth. Whisk in Dijon mustard.
Scrape up any browned bits from the bottom of the pan for extra flavor.
Simmer: Let the sauce bubble for 2–3 minutes to reduce slightly. If using, stir in butter until melted for a smoother, slightly richer finish.
Finish: Return chicken and any juices to the pan. Spoon sauce over the pieces and simmer 1 minute.
Stir in chopped parsley. Taste and adjust salt and pepper.
Serve: Plate with extra parsley and lemon slices if you like. Spoon more sauce over the top.