Chef John's Zombie Meatloaf

Ingredients

• 1/2 cup unsalted butter
• 1 1/2 cups diced yellow onion
• 1/2 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
• 1/2 teaspoon dried thyme
• 1/4 teaspoon cayenne pepper
• 3 pounds lean ground beef
• 3/4 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
• 1/4 cup barbeque sauce
• 1/4 cup ketchup
• 1 dash hot sauce, or to taste