Preheat oven to 350°
Dice onion. Use as much or as little as you like.
To a small frying pan, add butter and begin sautéing the onions, till translucent and softened. Set aside to cool
In a large bowl, add ground beef, stuffing mix, egg, garlic, ketchup, milk, pecorino cheese, seasonings (salt, pepper, and Italian seasonings), and about 2-3 tablespoons of that jarred brown gravy. Add the onions once they are cooled. Mix extremely well.
Line two loaf pans with parchment paper to make for easier removal!
With the 1.5 lb of meat you should be able to fit two loaf pans perfectly. Fill them with the meat mixture and place on a baking sheet.
Bake for 45-50 mins.
Remove and brush on some of that brown gravy. Return to oven for 10-15 more minutes. Internal temp should be above 165°
Heat up the remaining gravy and brush over the cuts of the meatloaf and over mashed potatoes.