Turn salmon and liquid into a medium mixing bowl. Flake with a fork, removing OR mashing any bones (they are edible). Mix in grated onion, parsley and pepper. Mix beaten eggs with salmon. Add enough bread crumbs, about 1/2 to 3/4 cup, to make thick enough to shape into 12 small patties. Roll patties in 1/2 cup bread crumbs. In a large heavy skillet over low heat, melt 2 tablespoons of butter; add patties. Fry patties slowly on one side; add remaining butter, turn patties and fry until brown on the other side.