While you get your grill or pan heating, prepare all your vegetables and ingredients for efficiency. Halve the cherry tomatoes lengthwise, dice the cucumber into 1/2-inch cubes, finely dice the red onion, chop the fresh parsley, and crumble or have your feta ready. In a small bowl, whisk together the extra virgin olive oil, red wine vinegar, lemon juice, Dijon mustard, oregano, salt, and pepper until emulsified. I prefer to make the dressing ahead of time so the flavors can meld while the other components cook. Set the dressing aside at room temperature.

Bring a large pot of salted water to a boil and cook the rotini according to package directions until al dente. Drain the pasta thoroughly and spread it on a sheet pan or in a large bowl to cool slightly while you cook the chicken. I like to let the pasta cool a bit before mixing it with the dressing so it doesn't get mushy and can better absorb the vinaigrette.

Pat the pounded chicken breasts dry with paper towels, then coat both sides generously with avocado oil, salt, and pepper. Heat a grill or large skillet over medium-high heat until very hot. Grill or pan-sear the chicken for 8-10 minutes per side until golden brown and the internal temperature reaches 165°F. The pounded thickness ensures even, quick cooking without drying out the meat.

Transfer the cooked chicken to a cutting board and let it rest for 5 minutes to retain its juices. Once cooled slightly, cut the chicken into bite-sized pieces or chunks, roughly 1-inch cubes. This allows the warm chicken to absorb some of the dressing flavor while you finish assembling the other components.

In a large bowl, combine the cooled pasta from Step 2, chopped chicken from Step 4, halved tomatoes, diced cucumber, diced red onion, pepperoncini, olives, and crumbled feta. Pour the prepared dressing from Step 1 over the salad and toss gently but thoroughly until all ingredients are evenly coated. Finally, sprinkle the fresh chopped parsley over the top and toss once more. Taste and adjust seasoning if needed.