Preheat the oven to 350°F/180°C. Grease a rimmed baking sheet.
Heat a skillet over medium high heat, heat oil and add onion and ground beef breaking it up with a wooden spoon until it’s no longer pink. Drain fat if it produces a lot of grease.
Add Worcestershire sauce, Dijon mustard, salt and pepper.
Add garlic and cook for 30 seconds.
Season with salt and pepper if needed, and remove from heat.
Cut the rolls in half, place the bottom half on the prepared baking sheet, and layer the meat mixture, followed by the cheese slices.
Place the top half of rolls, brush with melted butter and sprinkle with sesame seeds.
Bake for 15 minutes or until the rolls are golden, and the cheese has melted.