Preheat and prep: Heat the oven to 350°F (175°C). Line a 9x13-inch baking dish or sheet pan with parchment for easy cleanup.
Split the buns: Use a serrated knife to slice the buns horizontally as one slab. Keep the bottoms and tops intact to assemble easily.
Mix the spread: In a small bowl, stir together the Dijon mustard and mayonnaise.
Spread evenly over the cut side of the bottom buns.
Layer the cheese: Lay half of the cheese slices over the bottom buns. Cover the surface corner to corner.
Add the turkey: Arrange the turkey evenly over the cheese. Season lightly with salt and pepper.
If using stuffing, sprinkle it over the turkey.
Cranberry layer: Spread the cranberry sauce in a thin, even layer over the turkey. If it’s very thick, loosen with a teaspoon of water so it spreads easily.
Top with more cheese: Add the remaining cheese slices. This helps the sliders hold together when you pull them apart.
Cap the sliders: Place the top bun slab over the filling.
Make the butter topping: In a small bowl, combine melted butter, Worcestershire, poppy seeds, garlic powder, onion powder, herbs (if using), and a pinch of salt and pepper.
Brush generously: Brush the butter mixture over the tops, letting it drip down the sides.
Use all of it for maximum flavor.
Bake covered: Tent loosely with foil and bake for 12–15 minutes until the cheese is melted and the sliders are heated through.
Finish uncovered: Remove the foil and bake 5–7 more minutes until the tops are lightly golden and slightly crisp.
Slice and serve: Let rest 3–5 minutes. Cut along the bun lines and serve with warmed gravy on the side for dipping, if desired.