Foil Pack French Dip Sandwiches

Name: Foil Pack French Dip Sandwiches
Prep time: 10 min
Cook time: 10 min
Total time: 20 min
Cuisine: American
Ingredients: 1/2 cup (8 tablespoons) unsalted butter (softened to room temperature); 1 package au jus gravy mix (divided); 1 teaspoon Worcestershire sauce; 3/4 teaspoon dried minced garlic; 1/2 teaspoon onion powder; Heavy Duty Foil; 1 long/large (or 2 smaller) baguettes; 1 pound deli roast beef ((ask for rare, since it's getting cooked)); 1 package pre-sliced (12 slices total) provolone cheese