Take chicken breasts out of the fridge and let them come to room temperature.: You'll notice the chill leave the surface and the meat relaxes, which helps it cook evenly and prevents a band of overcooked outside with a cool center. The texture becomes juicier when the internal temperature is closer to room temperature before cooking. If you skip this, the exterior may brown too quickly while the center remains underdone. A common mistake is leaving meat out too long, so aim for about 15 to 20 minutes to avoid food safety concerns.
Preheat oven to 375 F/190 C and spray baking dish with non-stick spray. (I used a dish that was 8" x 11" but something close to that will work fine.): You'll feel the kitchen warm and watch the oven dial or display reach temperature, ensuring consistent baking. Preheating ensures the dish begins cooking immediately and helps the topping bubble properly. Not preheating can extend bake time and produce uneven doneness. Avoid using an incorrectly sized pan that crowds the chicken , which can trap steam and prevent browning.
Drain can and chop the black olives, chop green olives, chop red onion, and chop capers.: As you chop, you'll see contrasting colors and smell the briny notes of the olives and capers . Uniform chopping helps the flavors distribute evenly over each bite. If pieces are uneven, some bites will be overly salty or too mild. Rinse capers only if you need to reduce sodium, but pat everything dry to avoid diluting the topping.
Mix chopped black olives, green olives, red onion, and capers with Dijon mustard, garlic, lemon juice, and 2 T olive oil to make the topping.: Once combined, the topping should look cohesive and glossy, with tiny flecks of garlic and onion. The mustard and oil emulsify the mixture so it clings to the chicken while baking, and the lemon lifts the whole profile. If the mixture seems watery, a bit more mustard or oil helps bind it. A frequent error is under mixing, which leaves the mustard and oil separated, reducing adhesion to the meat.
Trim chicken as needed and season with Poultry Seasoning (affiliate link) and a little salt and pepper.: Trimming creates even surfaces and removes excess fat, producing a cleaner sear. You should see the seasoning adhere visibly to the surface. Season evenly so every strip gets flavor. Beware of over salting since the topping adds saltiness as it bakes.
Heat other 1 T olive oil in a large frying pan and brown the chicken about 5 minutes per side, or just until it's nicely browned. (It will not be fully cooked at this point.): The pan will sizzle and aromas of caramelized meat will develop, creating that desirable golden crust. Browning builds flavor through the Maillard reaction and helps seal juices. If the oil smokes, lower the heat to avoid bitter flavors. A common slip is moving the chicken too soon, which prevents proper crust formation.
Cut chicken into 3 or 4 lengthwise strips (Make 4 strips for large chicken breasts or 3 for smaller ones. You want the strips to be about the same thickness.): Notice the firm texture and the clean edges as you slice, which makes the portioning consistent for even baking. Similar thickness ensures uniform cooking times and an attractive final presentation. If strips vary widely, some pieces can overcook while others stay underdone. Use a sharp knife for clean cuts and safety.
Arrange chicken strips in a baking dish. (I used a dish that was 8" x 11" but any size close to that will work.: Lay the strips so they sit comfortably without overlapping, which lets heat circulate and the topping contact the surface. You'll see the browned sides facing up and the pieces leveling in the dish. Crowding leads to steaming, which prevents the topping from crisping slightly. If you notice overlapping, use a larger dish or two smaller dishes.
Spoon the olive and caper sauce over the chicken, trying to get all the pieces of chicken covered with sauce.: The topping should glisten as you spread it, coating each strip so every bite delivers briny flavor. Press gently to help the sauce adhere and to nestle small pieces into crevices. If you heap it all in one spot, coverage becomes uneven and some bites lack balance. A frequent misstep is skimping on distribution, leaving parts of the chicken bare.
Bake 20 -25 minutes, or until the chicken is cooked through and the whole dish is bubbling hot.: During baking you will hear gentle bubbling and see the topping thicken and the pan juices shimmer. This stage melds flavors and finishes cooking the meat. If it bakes too long, the chicken can dry out, so check early. Underbaking is a safety concern, so ensure it reaches the right internal temperature.
I would use an Instant Read Meat Thermometer (affiliate link) if you have one to check that chicken has reached a temperature of 165 F/75 C after 20 minutes, and cook it a few minutes longer if needed.: The thermometer gives an exact reading, removing guesswork, and a quick probe tells you when the chicken is safely done. Insert into the thickest part without touching bone to get an accurate result. A misread can occur if probe touches the pan, so avoid that mistake.
Serve hot, with the sauce and pan juices spooned over the chicken strips when you plate it.: You will notice steam rising and the sauce coating the chicken , creating glossy, appetizing servings. Spoon the pan juices over each piece so every bite is moist and flavorful. Letting it sit too long before serving cools the sauce and dulls flavors, so plate promptly.