In tall narrow pot, gently heat stock until body temperature. Meanwhile, in a large bowl, stir together vegetables, parsley, and meat until well combined; add salt and pepper; fold in egg whites.
Whisk heat stock into egg mixture; return to pot and, whisking, bring slowly to boil. When mixture begins to look frothy, stop stirring to allow egg mixture to rise and solidify into a raft. Lower heat to medium-low. Carefully make a vent hole in raft with spoon handle. Simmer consommé gently for 30 minutes.
Leaving pot on heat, carefully push raft down with back of ladle; ladle clarified consommé through cheesecloth-lined sieve into clean pot. Heat until very hot. Stir in Port.
Garnish: Slice scallops crosswise into 3 pieces, place 3 discs into bottom of each of 6 warmed bowls. Pour hot consommé over scallops; arrange celeriac and cucumber decoratively in each bowl. Serve immediately.