01 -
Cut the onion in half, then slice it thinly. Warm olive oil and butter in a skillet over medium-low heat. Toss in the onions along with a small pinch of salt (about 1/4 teaspoon). Stir off and on for roughly 45 minutes, letting them turn a deep golden color.
02 -
Mix the au jus following the directions on the packet. Set aside once ready.
03 -
Without separating them, slice the Hawaiian rolls horizontally so you’ve got one sheet for the tops and another for the bottoms.
04 -
Quarter the cheese slices. Lay two quarters on each bottom roll. Fold slices of roast beef, adding two folds over the cheese on each slider. Spread the caramelized onions evenly across each. Drizzle a bit of au jus (about 1/2 teaspoon) on the onions, add two more cheese quarters, and finish by placing the roll tops back on.
05 -
Brush a thin coating of au jus over the tops of the rolls, adding some fresh thyme if using. Don’t cover with foil to keep the roll tops from sticking.
06 -
Pop the sliders into an oven preheated to 350°F (180°C) and bake them on the middle rack. Cook for 20-25 minutes, letting the cheese soften and the tops turn golden. Serve them up with the leftover au jus on the side.