Preheat the oven to 450°F (232°C). Line a rimmed baking sheet or casserole dish with parchment paper.
In a medium mixing bowl, combine the softened cream cheese, shredded cheddar, ranch seasoning, and Worcestershire sauce. Blend until the mixture is smooth and homogeneous.
Lay the chicken breasts flat on a cutting board. Using a sharp paring knife, slice a horizontal pocket into the thickest side of each breast, ensuring you do not cut all the way through to the other side or the back.
Evenly divide the cream cheese mixture and stuff it into the chicken pockets. Use toothpicks to seal the opening if the pocket is overfilled.
In a small ramekin, whisk together the garlic powder, onion powder, smoked paprika, black pepper, and salt.
Place the chicken breasts in the prepared dish. Brush the exterior of the chicken with the melted butter and season generously on both sides with the spice blend.
Bake for 25 to 30 minutes, or until the internal temperature of the chicken meat reaches 165°F (74°C) on an instant-read thermometer.
Remove from the oven and allow the chicken to rest for 5 minutes. Garnish with fresh parsley and drizzle any remaining pan butter over the top before serving.