Follow these detailed steps carefully for foolproof, bakery-quality biscuit sliders. The process is divided into making the biscuits, preparing the filling, and the final assembly and baking.

Part 1: Crafting the Perfect Cheddar Chive Biscuits

1. Preheat and Prepare: Preheat your oven to 400°F (200°C). Line a large baking sheet with parchment paper to prevent sticking and ensure easy cleanup.
2. Combine Dry Ingredients: In a large mixing bowl, whisk together the all-purpose flour, granulated sugar, baking powder, salt, and garlic powder. Ensuring these are well-combined is crucial for an even rise.
3. Cut in the Butter: Add the cold, cubed butter to the flour mixture. Using a pastry blender, two knives, or your fingertips, cut the butter into the flour until the mixture resembles coarse crumbs with some pea-sized pieces of butter still visible. This is the secret to flaky layers, so work quickly to keep the butter from melting.
4. Add Cheese and Chives: Gently stir the 1 ½ cups of grated sharp cheddar cheese and the chopped fresh chives into the flour and butter mixture. Distribute them evenly without overworking the mixture.
5. Incorporate Buttermilk: Create a well in the center of your dry ingredients and pour in the cold buttermilk. Use a fork or a rubber spatula to mix until a shaggy, slightly sticky dough just comes together. Be careful not to overmix; a few dry spots are perfectly fine.
6. Knead and Fold (The Lamination Step): Turn the dough out onto a lightly floured surface. Gently press it into a rough rectangle. Fold the dough in on itself like a letter (one-third over, then the other third over that). Rotate the dough 90 degrees and repeat this pressing and folding process 3-4 more times. This step builds the beautiful, flaky layers.
7. Shape the Biscuits: Gently pat the dough out into a rectangle that is about ½ to ¾-inch thick. Using a 2.5-inch round biscuit cutter, press straight down to cut out your biscuits. Do not twist the cutter, as this can seal the edges and prevent them from rising properly. Place the cut biscuits onto the prepared baking sheet, ensuring they are just touching. This helps them rise upwards instead of outwards.
8. Bake the Biscuits: Bake for 15-18 minutes, or until the biscuits are tall, golden brown, and cooked through. The cheese will be slightly crispy on the edges. Remove from the oven and let them cool on the baking sheet for a few minutes before transferring them to a wire rack.

Part 2: Preparing the Savory Filling

1. Season the Beef: In a medium bowl, combine the ground beef, Worcestershire sauce, black pepper, and onion powder. Use your hands to gently mix the ingredients until just combined. Overworking the meat can result in tough patties.
2. Form the Patties: Divide the beef mixture into 8 equal portions and shape them into thin patties, slightly larger than the diameter of your biscuits, as they will shrink during cooking.
3. Cook the Patties: Heat a large skillet or griddle over medium-high heat. Cook the beef patties for 3-4 minutes per side, or until cooked through and nicely browned. Transfer the cooked patties to a plate lined with a paper towel to drain any excess grease.

Part 3: Assembly and Final Bake

1. Lower Oven Temperature: Reduce your oven temperature to 350°F (175°C).
2. Slice the Biscuits: Once the biscuits are cool enough to handle, use a serrated knife to carefully slice each one in half horizontally, like a hamburger bun.
3. Layer the Sliders: Arrange the bottom halves of the biscuits in a 9×13-inch baking dish or back onto the parchment-lined baking sheet. Layer the ingredients in the following order on each biscuit bottom: one slice of deli ham, one cooked beef patty, and a half-slice of provolone or Swiss cheese.
4. Top the Sliders: Place the top half of each biscuit onto the layered filling.
5. Prepare the Topping: In a small bowl, whisk together the melted butter, Dijon mustard, dried parsley, and optional poppy seeds until well combined.
6. Brush and Bake: Generously brush this butter mixture over the tops of all the assembled sliders, allowing some to drip down the sides. This not only adds incredible flavor but also helps to create a beautifully golden and slightly crispy crust.
7. Final Bake: Place the baking dish in the preheated oven and bake for 8-10 minutes, or until the cheese is fully melted and bubbly, and the tops of the sliders are golden brown and toasted.
8. Rest and Serve: Let the sliders rest for a minute or two before serving. This allows the cheese to set slightly, making them easier to handle. Serve immediately while warm and gooey.