Preheat oven to 350 degrees. Spray muffin tin cups with cooking spray.
In a small bowl, soak panko breadcrumbs in milk, allowing it to absorb completely.
Finely chop onion and red bell pepper. Mince Italian parsley and garlic cloves.
Place ground meat and sausage in a large bowl. Add soaked breadcrumbs, onion, bell pepper, parsley, garlic, hot sauce, mustard, egg, salt, and pepper to the bowl, then gently mix with clean hands, until combined.
For the glaze, stir together ketchup, mustard, vinegar, brown sugar, and hot sauce in a small bowl. Add salt and pepper to taste.
Evenly divide the mixture into 12 muffin cups. Press lightly into cups. They will fill slightly above the rim.
Bake for 15 minutes, then spread a spoonful of glaze over the top. Place back into oven for 15 to 20 more minutes, until cooked through.
Remove from oven and let rest 5-10 minutes before serving with remaining glaze and a sprinkle of Italian parsley.