Stir in the ground meats and the milk mixture to make a creamy filling.
Preheat the oven to 400 °F. Lightly oil a 9 or 10" baking dish.
Spoon a thin layer of the tomato sauce over the bottom, and cover with a layer of celery.
Spread the filling over the celery, then the rest of the tomato sauce, and finish by sprinkling with the remaining grated Parmesan. (if you have enough for a second layer, repeat the steps but set the celery stalks at a 90-degree angle to the first layer, so they form a woven pattern. Cover with filling and sauce and finish with grated Cheese.)
Bake for 30 to 40 minutes, until the top is dappled golden brown and is brown at the edges. Serve hot or at room temperature. Ciao