1. Preheat the Oven and Prepare the Buns
Start by preheating your oven to 350°F (175°C). This will ensure that your sliders bake evenly and get that perfect golden color. While the oven is heating up, cut the slider buns in half horizontally. You’ll have both the top and bottom pieces of each bun. Place the bottom halves of the buns in a greased casserole dish or a baking pan. Make sure the buns are close together to help them hold their shape during baking.

2. Spread the Mayo and Dijon Mustard Mixture
In a small bowl, mix the mayonnaise and Dijon mustard together. This mixture adds a nice creamy, tangy layer to the sliders, balancing out the richness of the ham and cheese. Spread this mayo and mustard combination evenly over the bottom buns in the casserole dish. Make sure to cover the entire surface to ensure every bite has that delicious flavor.

3. Layer the Ham and Cheese
Next, take the slices of deli ham and layer them evenly over the mayo and mustard-covered buns. You can slightly overlap the ham slices to make sure each slider has a generous amount of ham. Once the ham is layered, top it with the slices of Swiss cheese. The cheese should cover the ham entirely, creating a gooey, cheesy filling that will melt beautifully during baking.

4. Place the Top Buns
After layering the ham and cheese, place the top halves of the slider buns on top. These will be the crown of the sliders, so make sure they’re placed gently to avoid squishing the filling. The buns will absorb the buttery sauce, giving them a crispy texture and rich flavor when they bake.

5. Prepare the Butter Sauce
In a small bowl, combine the melted butter, onion powder, Worcestershire sauce, and poppy seeds. Stir everything together until well-combined. This butter sauce is what makes these sliders so irresistible. The Worcestershire sauce adds a savory, umami flavor, while the onion powder brings a subtle sweetness. The poppy seeds add a delightful crunch and a touch of nuttiness. Once the sauce is ready, pour it evenly over the top of the assembled sliders. Be sure to cover each bun so that every bite will have that crispy, buttery coating.

6. Bake the Sliders
Cover the casserole dish with aluminum foil to help the sliders cook evenly. Place the dish in the preheated oven and bake for 10 minutes. The foil will help the cheese melt without over-browning the buns. After 10 minutes, remove the foil and continue baking for another 10 minutes, or until the sliders are golden brown and the cheese is fully melted. Keep an eye on the sliders as they bake to ensure they don’t burn.

7. Slice and Serve
Once the sliders are baked to perfection, remove them from the oven and let them cool for a few minutes. Use a sharp knife to cut them into individual sliders. Serve them warm, and enjoy the delicious combination of savory ham, melty cheese, and crispy, buttery buns. These sliders are best enjoyed fresh out of the oven, but they can also be stored in an airtight container for a day or two and reheated.