Preheat the oven to 350 degrees F. Lightly grease a loaf pan and set it aside.

In a large bowl, combine 6 cloves of garlic, the minced onion, egg, egg yolk, half and half, 2 tablespoons of parsley, and 1/4 cup of the Parmesan cheese. Stir until everything is well mixed.

Add the ground chicken, Italian chicken sausage, 1 teaspoon of salt, and the pepper. Gently mix until just combined. Fold in the breadcrumbs and shape the mixture into a loaf.

Place the meatloaf into the prepared pan and sprinkle the top evenly with 1 1/2 tablespoons of the remaining Parmesan cheese.

Bake for 35 to 40 minutes, or until the internal temperature reaches 165 degrees F. Remove from the oven and let it rest while you prepare the sauce.

Heat 1 tablespoon of olive oil in a small saucepan over medium-high heat. Add the remaining 2 cloves of garlic and cook for about 1 minute, just until fragrant.

Pour in the white wine and chicken broth. Bring to a boil, then lower the heat and let it simmer until reduced by about three quarters, leaving roughly 1/3 cup of liquid.

Turn off the heat and slowly whisk in the cold butter cubes until smooth. Stir in the remaining Parmesan cheese, parsley, remaining salt, and crushed red pepper.

Slice the meatloaf and serve warm with the garlic butter sauce drizzled over the top.