In a large mixing bowl, combine 1 lb ground chicken, 1 cup Italian breadcrumbs, 1/2 cup grated Parmesan cheese, 1 tsp garlic powder, 1 tsp onion powder, 1 tsp dried oregano, 1/2 tsp salt, 1/4 tsp black pepper, and 1 egg. Mix gently until just combined.
Divide the mixture into 8 equal portions and form into small, slider-sized patties.
Heat a skillet over medium heat with a little oil. Cook the patties for about 4-5 minutes per side until golden brown and cooked through (internal temperature 165°F). Remove from heat and set aside.
In a small saucepan, melt 1/4 cup unsalted butter over low heat. Stir in 1 cup marinara sauce until smooth and heated through to make marinara butter.
Preheat oven to 375°F (190°C). Slice slider buns in half horizontally. Arrange bottom halves in a baking dish and brush generously with marinara butter.
Place a chicken patty on each bun bottom, then top with shredded mozzarella cheese.
Bake sliders for about 10 minutes until cheese is melted and bubbly.
Remove sliders from oven. Brush tops of buns with remaining marinara butter and place on sliders. Garnish with fresh basil leaves before serving.
