Prep the chicken: Slice each chicken breast horizontally to make thin cutlets. Pat dry.
Season both sides with salt, pepper, and garlic powder. Lightly dredge in flour, shaking off excess.
Sear the cutlets: Heat olive oil in a large skillet over medium-high. Add chicken and cook 3–4 minutes per side until golden and just cooked through.
Transfer to a plate; tent loosely with foil.
Sauté the garlic: Reduce heat to medium. Add butter to the same pan. Stir in minced garlic and cook 30–45 seconds until fragrant, not browned.
Deglaze: Pour in chicken broth and scrape up any browned bits.
Let it simmer for 1–2 minutes to reduce slightly.
Make the sauce: Stir in heavy cream, Dijon (if using), a pinch of red pepper flakes, and lemon zest. Simmer gently 2–3 minutes, stirring often, until slightly thickened.
Add the cheese: Reduce heat to low. Sprinkle in Parmesan a little at a time, stirring until smooth.
If the sauce seems too thick, add a splash of broth or cream to loosen.
Finish and balance: Add 1 teaspoon lemon juice, taste, and adjust with more salt, pepper, or lemon as needed. You want creamy, savory, and bright.
Return the chicken: Nestle cutlets back into the sauce and spoon sauce over the top. Simmer 1 minute to warm through.
Garnish and serve: Sprinkle with chopped parsley or basil.
Serve over pasta, rice, or mashed potatoes, or with crusty bread to mop up the sauce.