Preheat the oven to 350 degrees and line a rimmed baking sheet with a rack. Season the chicken with salt, pepper and the cajun seasoning. In a large skillet, heat 2 tablespoons extra-virgin olive oil and brown the chicken on each side for about 2 minutes; transfer to a plate and reserve the skillet. Cut the puff pastry into 4 equal pieces and roll each one out into an 8-inch square. Place a chicken breast onto each of the squares toward one corner; top each with a brie slice and 1 tablespoon bacon. Fold the pastry in half to create a triangle and pinch closed along the edges. Brush with the chicken drippings from the skillet. Using a sharp knife, make 2 small, straight cuts on top to allow the steam to vent. Bake until the chicken is cooked through, 30 to 35 minutes.