To prepare the Greek salad dressing, put the olive oil, vinegar, minced garlic, fresh lemon juice, dried basil, mustard, yogurt, sugar, dried oregano, black pepper, and salt in a mason jar.
Whisk them until well combined.
To prepare the chicken, use the dressing you prepared to get a Greek marinade.
Marinate the chicken breasts or chicken thighs for as long as possible. The longer it marinates, the better. You can use it right away if you do not have time.
Sear the chicken on medium-high heat for about 4-5 minutes on each side or until cooked.
Let the chicken rest on a cutting board and come to room temperature before slicing.
Meanwhile, prepare the salad. Set the Romain Lettuce or iceberg lettuce in a large bowl, then top it with cucumbers, tomatoes, red onions, feta cheese, golden Greek pepperoncini, and Greek Kalamata olives.
Finally, on top of the salad place the chicken slices and the dressing.
Serve and enjoy!