Preheat the oven to 350℉ (176℃). Combine the ingredients for the white sauce in a small bowl and whisk until smooth.
Cut the brisket into bite-size pieces or chop it into a small-dice and toss the beef with BBQ sauce.
Cut the Hawaiian rolls in half by using a bread knife to slice through the whole sheet. Spread the reserved white sauce on either side of the rolls.
Add brisket to the rolls and cover with the tops. Place the sheet into a baking dish.
Brush the top of the rolls with melted butter using a pastry brush and garnish with poppy seeds.
Bake for 15-20 minutes until soft and heated through.
Visit my website for the full recipe and more like it.