Place the bread cubes in a large mixing bowl and pour over the stock to moisten. It should be thoroughly moistened, but not soggy. Peel the onions and cut in half lengthwise. Slice, crosswise, into 1/2″ slices. Trim the tough tops and root ends from the leeks. Slice, lengthwise, 3/4ths of the way through. Wash thoroughly, holding the layers apart to remove all of the grit. Slice, crosswise, into 1/2″ slices Peel the garlic and lightly crush the cloves, Slice the celery into 1/2″ slices. Place all of the vegetables in a single layer on heavy baking sheets. Toss with the olive oil. (There should be just enough to coat.) Place in a preheated 450 °F. oven for 12 to 15 minutes. Stir twice so the vegetables on the edge won’t get too brown. Remove and cool. Place on a cutting board and chop into a fine dice. Add to the bread mixture. Add the parsley. Beat together the eggs and the whites. Toss into the mixture with the seasonings. (To correct the seasonings, cook a small amount in the microwave and taste.) Spray 1 or 2 shallow baking dishes with non-stick vegetable spray. Bake in a preheated 375 °F. oven until hot through and lightly browned….45 minutes to 1 hour. Makes 12 to 16 servings.