Preheat oven to 375°F and line a baking dish with foil.
In a large bowl, mix together ground turkey, beaten egg, chopped onion, bread crumbs, salt, pepper, garlic powder, cooking sherry, and steak sauce until well combined.
Form the mixture into medium-sized meatballs (about 16 total) and place on the prepared foil-lined baking dish.
Dash the meatballs with adobo seasoning and bake for 40 minutes or until cooked through and internal temperature reaches 165°F.
During the last 10 minutes of meatball cooking time, warm the French bread in the oven until crusty.
Cut each loaf of bread lengthwise to create a top and bottom.
Place a layer of cooked meatballs on the bottom half of each bread loaf.
Spread spaghetti sauce evenly over the meatballs.
Top generously with shredded mozzarella cheese.
Reduce oven temperature to 325°F and return subs to oven until cheese melts, about 5-7 minutes.
Cut each loaf in half to serve 4 portions total.