Preheat the oven to 350°F.
Lightly coat a 9x13-inch baking dish with nonstick cooking spray and set aside.
Place the softened cream cheese in a 4- to 5-quart heavy-bottom stock pot over medium heat.
Stir the cream cheese frequently until fully melted and smooth.
Add the dry ranch dressing mix, onion powder, and freshly cracked black pepper to the melted cream cheese.
Stir until the seasonings are evenly incorporated.
Remove the pot from the heat.
Add the sliced green onion, shredded cooked chicken, crumbled bacon, and 1 cup of the shredded cheddar cheese.
Stir until the chicken mixture is fully combined and evenly coated with the cream cheese mixture.
Place the bottom half of the Hawaiian rolls into the prepared baking dish.
Spread the chicken ranch mixture evenly over the bottom layer of rolls.
Sprinkle the remaining 1 1/2 cups shredded cheddar cheese evenly over the chicken mixture.
Place the top half of the Hawaiian rolls over the shredded cheese layer.
Brush the melted butter evenly over the tops of the rolls using a pastry brush.
Sprinkle the grated Parmesan cheese evenly over the buttered rolls.
Sprinkle the finely chopped fresh chives evenly over the Parmesan layer.
Cover the baking dish with aluminum foil.
Bake for 25 minutes.
Remove the aluminum foil.
Continue baking for an additional 5 to 8 minutes, or until the tops are golden brown and the cheese is melted.
Remove the baking dish from the oven.
Allow the sliders to rest for 5 minutes before slicing into individual servings.
Serve warm.