Preheat your oven to 400°F (200°C). Line a large, rimmed baking sheet with parchment paper or aluminum foil for easy cleanup. If using foil, lightly spray it with cooking spray.

Dry the Chicken: Remove the chicken thighs from their packaging and place them on a cutting board. Use paper towels to carefully pat the chicken thighs thoroughly dry. Removing excess moisture is crucial for achieving a nice crust.

Mix the Rub: In a small mixing bowl, combine the dry Ranch seasoning mix, garlic powder, onion powder, black pepper, and the optional Parmesan cheese. Stir until all ingredients are uniformly mixed.

Coat the Chicken: Place the dried chicken thighs into a large bowl. Drizzle the 2 tablespoons of olive oil or melted butter over the chicken and toss lightly to ensure the thighs are evenly coated in the fat.

Season: Sprinkle the prepared Ranch seasoning rub generously over all the chicken pieces. Use your hands or tongs to ensure every surface of the chicken thigh is thoroughly covered in the spice mixture.

Bake: Arrange the coated chicken thighs on the prepared baking sheet in a single layer, ensuring they are not touching each other. Place the baking sheet into the preheated 400°F oven. Bake for 25 to 30 minutes.

Check Temperature: The chicken is fully cooked when the internal temperature reaches 165°F (74°C) as measured by an instant-read meat thermometer inserted into the thickest part of the thigh.

Rest: Once cooked, remove the baking sheet from the oven and allow the chicken thighs to rest for 5 to 10 minutes before serving. Garnish with fresh chopped parsley, if desired, and serve immediately.