1Preheat the oven to 350 degrees F (180 degrees C) and lightly grease a loaf pan.
2Combine 6 cloves minced garlic, onion, egg, egg yolk, half and half, 2 tablespoons parsley, and 1/4 cup grated Parmesan in a bowl; mix until well combined.
3Add ground chicken, sausage, 1 teaspoon salt, and pepper; mix until combined.
4Fold in breadcrumbs until evenly mixed and form into a loaf shape.
5Transfer mixture into the prepared pan and sprinkle the top evenly with 1 1/2 tablespoons Parmesan cheese.
6Bake in the preheated oven until the internal temperature reaches 165 degrees F (73 degrees C).
7Let meatloaf rest.
8Heat 1 tablespoon olive oil in a small saucepan over medium-high heat. Add remaining 2 cloves garlic and cook until fragrant.
9Pour in wine and broth and bring to a boil. Reduce heat and simmer until reduced by about 3/4.
10Turn off heat and gradually whisk in cubed butter. Stir in remaining Parmesan cheese and parsley. Season with remaining salt and crushed red pepper flakes.
11Slice meatloaf and serve drizzled with garlic butter sauce.