Using a large skillet, add butter and olive oil. Place over medium-high heat until butter melts.

Add onions; cook, stirring occasionally, for 5-7 minutes, or until onions begin to soften.

Add sugar and salt; reduce heat to medium and continue cooking, stirring occasionally, for 10-15 more minutes, or until onions have are soft. (Note: If the onions begin to scorch or stick to the bottom of the pan, turn the heat down. The secret to caramelized onions is low and slow!)

Preheat oven to 350°F.

Spray a 9”x13” baking pan with nonstick spray.

Without separating rolls, split the package in half horizontally and place bottom half in the prepared baking pan.

Layer the the rolls with sliced roast beef, provolone cheese and caramelized onions. Place top half of the rolls on top. Using a sharp knife, cut sliders apart, but push sliders back together for baking.

In a small bowl, whisk together melted butter and Dijon mustard; brush this mixture evenly on top of rolls. Sprinkle chopped parsley on top of rolls.

Bake rolls for 10-12 minutes, or until cheese has full melted.

Meanwhile, make the Au Jus by adding the butter to a small saucepan; place over medium heat until butter has melted.

Add garlic and cook for 1 minute, stirring often.

Add beef stock, Worcestershire sauce, salt and pepper; stir until well combined and let simmer for 15 minutes.

Serve sliders with Au Jus Dip on side.