Roast Beef Panini with Au Jus

Ingredients (11)

• 2 pounds deli roast beef thinly sliced
• 8 pieces thick sliced sourdough bread
• 16-20 slices Havarti cheese sandwich sliced
• 2 small onions sliced into thin half circles
• 3 cups beef broth low sodium
• 1 (1-ounce) package Au Jus mix (I used McCormick brand)
• 3 tablespoons butter plus more for buttering the bread slices
• 1 tablespoon sugar
• 1 teaspoon Worcestershire sauce
• 1/2 teaspoon salt
• 1/4 teaspoon black pepper