In a large skillet, melt 3 tablespoons of unsalted butter over medium heat. Add thinly sliced medium onions and sauté for about 12-15 minutes, until they become soft and golden brown. Stir in fresh thyme, kosher salt, and black pepper to enhance the flavor. Once done, transfer the onions to a plate and set aside while you prepare the baking dish.

Preheat your oven to 350°F (175°C). Meanwhile, take your sweet rolls and slice them in half horizontally, keeping the bottom halves intact. Place the bottom half of the rolls cut-side up in an 11x7 baking dish. Make sure they fit snugly together, as this will hold all the delicious flavors of your French Dip Sliders.

Start building your sliders by layering half of the provolone cheese on the bottom halves of the rolls. Next, add a generous layer of sliced deli roast beef, followed by the sautéed onions you prepared earlier. Finally, top this with the remaining provolone cheese to ensure each slider is melty and indulgent. Place the top halves of the rolls over the filling.

In a separate bowl, mix the melted unsalted butter with the dried onion soup mix until well combined. Brush this flavorful mixture over the top of the rolls using a pastry brush, ensuring each roll is coated for that golden, crispy finish during baking. This step is crucial for infusing extra flavor into your French Dip Sliders.

Cover the baking dish with aluminum foil, being careful not to let it touch the tops of the rolls. Bake the sliders in the preheated oven for 25 minutes. After this time, remove the foil and bake for an additional 5 minutes, or until the tops are golden brown and slightly crispy. This creates the perfect texture for your sliders.

While the sliders are baking, prepare the au jus according to the package instructions using water. Heat it in a small saucepan over medium heat until it’s hot and slightly thickened. This savory dipping sauce is essential for the ultimate French Dip experience, complementing the rich flavors of the sliders wonderfully.

Once your French Dip Sliders are finished baking, take them out of the oven and let them cool for a couple of minutes. Garnish with freshly chopped parsley for a pop of color and added freshness. Serve the sliders warm alongside the au jus for dipping, inviting everyone to indulge in this delightful comfort food treat!