Chef John's Zombie Meatloaf

Ingredients

• 0.5 cup unsalted butter
• 1.5 cups diced yellow onion
• 0.5 cup diced celery
• 1 (8 ounce) package brown mushrooms, finely chopped
• 1 tablespoon kosher salt, divided
• 3 cloves minced garlic
• 1 teaspoon freshly ground black pepper
• 0.5 teaspoon dried thyme
• 0.25 teaspoon cayenne pepper
• 3 pounds lean ground beef
• 0.75 cup plain dry bread crumbs
• 1 egg, beaten
• 3 tablespoons buttermilk
• 2 tablespoons ketchup
• 1 tablespoon Worcestershire sauce
• 1 onion
• 2 whole cloves
• 1 pound bacon strips
• 0.25 cup barbeque sauce
• 0.25 cup ketchup
• 1 dash hot sauce, or to taste