Heat 4 tablespoons of olive oil in a 12-inch cast-iron skillet or large, heavy-bottomed skillet over medium-high heat.
Season the chicken breasts with salt and pepper on both sides. Dredge the chicken breasts in flour, lightly coating both sides and shaking off any excess. Place the chicken in the hot oil and cook for 5-7 minutes on both sides until golden brown. Transfer the chicken breasts to a paper towel-lined plate.
Melt two tablespoons of butter in the same skillet. Add the onion, bell pepper, and celery and cook for 3-5 minutes until the veggies begin to soften. Stir the veggies with a wooden spoon, scraping up any brown bits at the bottom of the pan. Add the garlic and cook for another minute until fragrant.
Add two tablespoons of flour to the skillet and cook while stirring for 1-2 minutes. Pour the chicken stock into the skillet while stirring constantly so that lumps do not form. Stir in the Worcestershire sauce and half and half, then add the onion powder, garlic powder, paprika, and cayenne pepper. Lower the heat to medium, season the gravy with salt and pepper to taste, and simmer for 2-3 minutes.
Transfer the chicken breasts back to the skillet with the gravy. Cover and simmer for 15-20 minutes until the gravy has thickened and the chicken is tender. Serve the chicken over white rice with gravy spooned over top. Enjoy!
You can also slice 3 large chicken breasts in half to give you 6 thinly sliced portions.
Leftover cajun smothered chicken can be stored in an airtight container for up to 3 days.