Preheat your oven to 350°F (175°C) and arrange the bottom halves of the Hawaiian rolls on a baking sheet.

Layer the tender brisket slices over the roll bottoms and place half a slice of Swiss cheese on each brisket piece.

Combine unsalted butter, Worcestershire sauce, Dijon mustard, dried onion flakes, garlic powder, and black pepper in a mixing bowl until smooth.

Spoon half of the butter mixture over the brisket and cheese layers, then drizzle on the white BBQ sauce.

Brush the remaining butter mixture over the tops of the roll caps and sprinkle poppy seeds evenly across the tops.

Bake in the preheated oven for 15–20 minutes, or until golden and cheese is melted, removing the foil towards the end.

Allow sliders to rest for 2-3 minutes before serving.