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 turned light golden brown. (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!)

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 warm Au Jus Dip on side.

Preheat oven to 350°F.

Slice baguette into 4 pieces. Using your fingers, tear out the center portion of each piece.

Using a small bowl, whisk together the melted butter, Dijon mustard and parsley. Brush/spread this mixture around the inside of each baguette piece.

Lay 3 slices of provolone on top of each other with a 1” overlap. Layer ¼ of the roast beef and ¼ of the caramelized onions on top of the cheese. Roll the cheese, roast beef and onion mixture up and then insert into the hollowed-out baguette. Repeat process with remaining ingredients.

Slice baguette chunks into 1” pieces. Line pieces up so that they are touching and then stand pieces up on a foil-lined sheet pan.

Using a small bowl, whisk all ingredients for the garlic butter together; brush mixture evenly on top of baguette.

Wrap foil around baguette. Bake for 20-25 minutes or until provolone cheese has completely melted.

Remove from oven and serve hot.