Preheat the oven to 400°F. Place a baking rack on a large sheet pan and set it aside.
In a medium bowl, combine the mayonnaise and mustard. In a separate medium bowl, combine the panko, dried breadcrumbs, garlic powder, salt, and black pepper.
Cut the chicken into twelve pieces. They should be approximately the same size as your slider buns. Place the cut chicken into the bowl with the mayonnaise and mustard and toss it to coat it evenly. Transfer the coated chicken pieces to the bowl with the breadcrumbs and toss them until they are evenly coated.
Place the chicken pieces on the baking rack with the sheet pan. Bake the chicken for approximately 20 minutes, or until the chicken reaches an internal temperature of 165°F.
To assemble the sliders, smear some mayo on the slider buns. Top with a piece of breaded chicken followed by a few pickle slices.