Follow these steps carefully to achieve perfectly cooked, flavorful lemon garlic chicken:

1. Prepare the Chicken: Pat the chicken breasts completely dry with paper towels. This is crucial for achieving a good sear. If the breasts are very thick (over 1 inch), you can either slice them in half horizontally to create thinner cutlets or place them between sheets of plastic wrap and gently pound them to an even thickness (about 3/4 inch). Pounding ensures faster and more even cooking.
2. Season and Dredge: In a shallow dish or on a plate, combine the all-purpose flour, 1 teaspoon of salt, and 1/2 teaspoon of black pepper. Whisk them together. Dredge each chicken breast in the flour mixture, coating all sides lightly. Shake off any excess flour. This light coating helps create a golden crust and slightly thickens the sauce later.
3. Heat the Pan: Place a large skillet (cast iron, stainless steel, or heavy-bottomed non-stick) over medium-high heat. Add the 2 tablespoons of olive oil. Allow the oil to heat up until it shimmers or a speck of flour sizzles instantly when dropped in. Getting the pan hot enough is key for a good sear.
4. Sear the Chicken: Carefully place the dredged chicken breasts into the hot skillet, ensuring not to overcrowd the pan (work in batches if necessary). Sear the chicken for 4-6 minutes per side, undisturbed, until golden brown and cooked through. The internal temperature should reach 165°F (74°C) when checked with a meat thermometer in the thickest part. Adjust cooking time based on chicken thickness. Don’t flip it too early; let the crust develop.
5. Remove Chicken: Once cooked, transfer the chicken breasts from the skillet to a clean plate. Tent loosely with foil to keep warm while you prepare the sauce. Don’t wipe out the skillet; those browned bits (fond) left behind are packed with flavor!
6. Sauté Aromatics: Reduce the heat under the skillet to medium. Add the 3 tablespoons of unsalted butter to the pan. Once the butter has melted and foamed slightly, add the minced garlic. Sauté the garlic for about 30-60 seconds, stirring constantly, until it becomes fragrant. Be very careful not to burn the garlic, as it will turn bitter.
7. Deglaze and Build Sauce: Pour in the 1/2 cup of chicken broth and the 1/4 cup of fresh lemon juice. Bring the mixture to a simmer, scraping the bottom of the pan with a wooden spoon or whisk to release all those flavorful browned bits (fond) into the liquid. This deglazing step is essential for a rich sauce.
8. Simmer and Thicken: Let the sauce simmer gently for 3-5 minutes, allowing it to reduce slightly and the flavors to meld. If using, stir in the lemon zest now. Taste the sauce and adjust seasoning if necessary, adding more salt or pepper if needed. If the sauce seems too thin, you can let it simmer a bit longer or mix 1 teaspoon of cornstarch with 1 tablespoon of cold water and whisk it into the sauce to thicken.
9. Return Chicken to Pan: Place the cooked chicken breasts back into the skillet, nestling them into the sauce. Spoon some of the sauce over the top of each chicken breast. Let the chicken simmer gently in the sauce for another 1-2 minutes, just to reheat and allow it to absorb some of the sauce’s flavor.
10. Garnish and Serve: Turn off the heat. Sprinkle the chopped fresh parsley over the chicken and sauce. Serve immediately, spooning extra lemon garlic sauce over the chicken and any accompanying sides.