Preheat oven to 425° F.
On a baking sheet, toss the potatoes with 2 tablespoons olive oil. Season with salt and black pepper. Slice onion and lay on pan.
In a bowl, toss together 2 tablespoons olive oil, the chicken, balsamic vinegar, dijon, oregano, paprika, garlic, salt and pepper.
Nestle the chicken around the potatoes and on the onions. Bake for 25-30 minutes, until the chicken is cooked through.
Meanwhile, combine the remaining ⅓ cup olive oil, the lemon juice, herbs, pepperoncini, olives, and sesame seeds. Mix the Tzatziki and feta.
Remove the chicken from the oven. Spoon the dressing over the chicken, potatoes and spring mix. Serve with the Tzatziki feta sauce. Enjoy!
