Pepperoncini Beef

Ingredients

• 5 pounds chuck roast
• 12 ounces beer
• 1 cup worchestershire
• 2 tablespoons gravy master
• 2 teaspoons salt and ground black pepper (kosher)
• 1 cup marinade (reserved)
• 16 ounces pepperoncini (and their juice)
• 1 tablespoon minced garlic
• 2 red onion (large)
• 2 tablespoons extra-virgin olive oil
• 2 tablespoons butter
• 2 teaspoons brown sugar
• 1/2 teaspoon salt and ground black pepper (each of kosher)