01 -
Melt the butter in a big pan on medium heat. Toss in the onion slices and coat them evenly. Stir every now and then for 12–15 minutes until the onions turn golden brown. Don't let them burn.
02 -
Mix in thyme, salt, and pepper with the onions. Stir everything gently, remove from heat, and set aside.
03 -
Turn the oven to 350°F. Slice the pack of rolls horizontally so they're split into tops and bottoms, but keep them connected. Lay the bottom half in an 11x7 pan, cut side up.
04 -
Place half the cheese slices on the rolls. Add the roast beef in an even layer. Spread the cooked onions over the beef, then add the rest of the cheese. Finish by placing the roll tops back on.
05 -
Combine the melted butter and onion soup mix in a small bowl. Use a brush to spread this mix evenly over the tops of the rolls.
06 -
Lightly cover the dish with foil, keeping it off the roll tops. Bake for 25 minutes. Take off the foil and bake another 5 minutes to crisp them up.
07 -
While the rolls are baking, prepare the au jus following the package instructions and using the water. Serve the sliders with the sauce on the side—chop a little parsley on top if you like.