Prepare the Chicken: Season the chicken thighs with garlic powder, onion powder, salt, and pepper. In a large skillet, heat the olive oil over medium heat. Add the chicken thighs and cook until golden brown and cooked through, about 5-7 minutes per side. Once done, remove from heat and let rest for a few minutes.
Make the Gravy: In the same skillet, add the chicken broth and bring to a gentle simmer. Stir in the brown gravy mix and whisk until the mixture thickens, about 2-3 minutes. Adjust salt and pepper to taste.
Combine Chicken and Gravy: Shred the cooked chicken thighs using two forks and return them to the skillet with the gravy. Mix until the chicken is well coated, then stir in the cheddar and mozzarella cheeses until melted and gooey.
Assemble the Sliders: Preheat your oven to 375. Slice the slider buns in half and place the bottom halves on a baking sheet. Spoon generous portions of the cheesy chicken gravy mixture onto each bun. Top with the other half of the slider buns.
Bake the Sliders: Cover the assembled sliders with foil and bake in the preheated oven for about 10 minutes. Remove the foil, and continue baking for an additional 5 minutes, or until the tops are lightly browned and the cheese is bubbling.
Serve: Remove from oven, garnish with chopped parsley, and serve hot. Enjoy your cheesy goodness!