Preheat oven to 350 degrees F.

In a small bowl, add the crackers, milk and three egg yolks, mix together and set aside to soak as you prepare the rest of the ingredients.

In a larger bowl, add the salmon and with clean hands or a fork mash and mush to break down the larger pieces. No need to mash to a paste but be thorough. Add and gently mix in onions, butter, lemon juice, parsley, salt and pepper, and the reserved cracker/milk/yolk mixture.

In a small bowl, beat the egg whites on high speed until stiff peaks form. Mix 1/3rd of the egg whites into the salmon mixture to lighten, then gently fold in the remaining egg whites in two additions.

Transfer to a greased 8×4-inch loaf pan or equivalent sized small casserole. Bake for 30 to 40 minutes (the loaf pan will generally take longer) or until the top is a golden brown and a knife inserted in the center comes out with just a bit of moisture but otherwise clean. Let stand for a few minutes before slicing.