Preheat the oven to 400℉ and a cast iron skillet over medium heat.
Mix the blackening seasoning together and sprinkle over the chicken, coating it generously on both sides. Lay out the bacon strips on a sheet pan and the bread tossed with olive oil and herbs on another.
Add the olive oil to the cast iron skillet and sear the chicken, about 2 to 3 minutes per side. Don't attempt to move it around while it sears, but do make sure to flip it before the sugar burns.
Transfer the skillet with the chicken to the oven, along with the bacon and croutons. All can cook together, the chicken for about 10 minutes (depending on how thick it is), the croutons for about 18 minutes, and the bacon for about 20 to 22 minutes. Check on them all often, especially watch the bacon so it doesn't burn. Check that the chicken reaches an internal temperature of 165℉.
Allow the chicken (and the bacon) to rest in the skillet for 5 or 10 minutes so they aren't too hot when you add them to the lettuce.
Wash and chop the lettuce, cucumber, and tomatoes and thinly slice the onion.
Add all ingredients for the dressing to a jar with a lid and shake well to emulsify.
Toss the lettuce with a bit of the dressing, then arrange it on a large platter topped with the sliced chicken, chopped bacon, croutons, tomatoes, cucumbers, onion, feta cheese and another drizzle of dressing. Serve while the chicken and bacon are still warm. Garnish with basil leaves.