Step 1

Put the butter in a big pan and melt it over medium heat.

Step 2

After adding the onions, coat them with the butter. Cook the onions over medium heat, tossing them regularly, for about 12 to 15 minutes, until they are tender and browned but not blackened.

Step 3

After adding the thyme, salt, and pepper, turn off the heat and set the mixture aside after stirring to blend the ingredients.

Step 4

Turn the oven up to 350 degrees Fahrenheit.

Step 5

Remove the rolls from their packaging while ensuring that they remain unbroken.

Step 6

To separate the tops from the bottoms of the rolls, use a broad knife to cut them lengthwise in the middle.

Step 7

Put the bottom, with the sliced side facing up, into a baking dish that is 11 by 7.

Step 8

Place one half of the cheese on top.

Step 9

The roast beef should be added.

Step 10

Place the onions on top, making sure they are well distributed.

Step 11

After that, sprinkle on the remaining cheese and finish by placing the top halves of the rolls on top.

Step 12

Combine the melted butter and onion soup mix in a low-volume bowl and swirl to combine.

Step 13

You may simply pour the butter sauce on top of the rolls if you want, but I find that brushing it on helps ensure that it is distributed evenly across the surface of the rolls.

Step 14

Bake for 25 minutes with the rolls covered in foil in a loose manner, taking care that the foil does not come into contact with the tops of the rolls.

Step 15

After removing the foil, continue baking the rolls for a further 5 minutes to brown them.

Step 16

While the rolls are in the oven, prepare the au jus by following the directions on the package and adding the water.

Step 17

The rolls should be served with a garnish of parsley as an alternative, and the au jus should be placed on the side for dipping.