In a skillet over medium heat, melt the butter.​

Add the diced onion, granulated sugar, and black pepper.​

Cook, stirring occasionally, until the onions are caramelized and golden brown, about 15 minutes.​

Remove from heat and set aside.​

Set your oven to 350°F (175°C).​

Grease a 9×13-inch baking dish or line it with parchment paper.​

Unroll one can of crescent dough and fit it into the bottom of the prepared baking dish, stretching to cover the entire surface.​

Press any seams together to seal.​

Evenly layer the roast beef slices over the dough.​Place the provolone cheese slices on top of the roast beef.​

Spread the caramelized onion mixture over the cheese layer.​

Unroll the second can of crescent dough and place it over the onion layer, stretching to cover completely.

Press the edges to seal and tuck in any excess dough.​

In a small bowl, beat the egg and mix in the dried onion soup mix, parsley flakes, and dried thyme.​

Brush this egg mixture over the top dough layer.​

Cover the dish with aluminum foil to prevent over-browning.​

Bake for 20 minutes.​

Remove the foil and continue baking for an additional 15 minutes, or until the top is golden brown.​

While the squares are baking, whisk together the au jus gravy mix and cold water in a saucepan.​

Bring to a boil over medium heat, then reduce to a simmer, stirring occasionally, until slightly thickened.​

Allow the baked dish to cool for about 5 minutes.

Cut into 12 squares.​

Serve warm with the prepared au jus on the side for dipping.