Why my Mom called this "Filling" I don't know because she never filled any thing with it! I assume this is a family recipe, my mom's family was from Italy and we have it EVERY Thanksgiving! I always make a lot as it is a great left-over and freezes well!
Since I make this on Thanksgiving the oven is already on. I usually just throw this in while cooking everything and keep checking on it until it looks right so temp and time is flexible.
I would guess pre-heat to 350?
Rinse gizzards and put them on to boil adding a pinch of salt. Keep an eye on them and add more water as needed, you want them to be cooked 'til tender.
Place a sleeve of crackers in a large ziploc bag and crush, dumping crumbs into a bowl large enough to mix all ingredients in. Repeat 'til you've crushed all 4 sleeves. Set aside.
Drain and rinse gizzards, allow to cool. Cut them in small pieces discarding the gristle part in the middle. Kitchen scissors work nice for this.
In a large skillet melt 1 stick of butter, add diced veggies and saute until tender. You don't want them to brown. Mean while beat eggs in a bowl and slowly add milk to crackers as you mix. You may not have to use all of milk, you want the mixture to be moist but not soggy. Once veggies are tender add eggs, turn off the heat, and stir constanly until eggs are soft set. You want this mix to be slightly soupy.
Pour egg mix and chopped gizzards into cracker mixture and stir until well combined.
Pour into a 9x13 baking pan and bake approx. 30 minutes or until top is golden brown.