French Dip Sandwich with Au Jus & Horseradish Herb Butter

Ingredients

• 2 pounds top sirloin or top block roast, room temperature
• 2 teaspoons kosher salt
• 2 cloves fresh garlic, peeled and crushed
• 1 teaspoon freshly ground black pepper
• 1 medium red onion, peeled and diced
• 1 quart beef broth
• 2 tablespoons unsalted butter
• 3 sprigs thyme, including the stems
• ½ teaspoon kosher salt
• Plus the drippings from the roast
• ½ cup unsalted butter (1 stick), room temperature
• ½ cup prepared horseradish
• 2 tablespoons fresh chives, very finely chopped
• ⅛ teaspoon freshly ground black pepper
• ½ pound provolone cheese, thinly sliced
• One and a half large loaves of french bread
• ¼ cup unsalted butter (½ stick)
• 2 sweet red peppers, de-seeded and thinly sliced
• 2 sweet orange peppers, de-seeded and thinly sliced