In a large mixing bowl, beat the egg and milk with a whisk.
Slowly fold in meat, cheese, oats, onions, and salt. Mix thoroughly with your hands.
Divide mixture into 8 equal portions and form 8 mini loaves, then place in a greased glass 9x13 dish or pan where they don't touch.
Put in the oven and bake for 20 minutes.
While your meatloaves cook for the first half, prep the sauce by mixing the ketchup, brown sugar, and mustard in a bowl.
After the loaves have been cooking for 20 minutes, remove from oven and top with the ketchup mixture. Put back in the oven and cook for an additional 25 minutes or until heated to 160°F.
Let cool for 5 minutes, then serve and enjoy!
You can also bake this recipe in a whole loaf, we just happen to think the mini loaves add to the magic. Be sure to extend the cooking time if you do it in a larger loaf! Start with 55 minutes total and cook until it's heated to 160°F.