Let egg whites stand, covered, in a large stainless-steel or glass mixing bowl at room temperature for 30 minutes. Meanwhile, cover a large baking sheet with parchment paper. Draw ten 2-1/2-inch circles or heart shapes on paper.
Preheat oven to 300 degrees F. Uncover eggs and add vanilla, cream of tartar, and salt. Beat with an electric mixer on medium speed until soft peaks form (tips curl). Add sugar, 1 tablespoon at a time, beating for 5 to 7 minutes on high speed or until stiff peaks form (tips stand straight) and sugar is almost dissolved (mixture will be stiff). Fold in chopped almonds.
Using a pastry bag fitted with a large star tip, pipe the meringue onto the circles or hearts on the paper, building the sides up to form shells.
Bake in preheated oven for 35 minutes. Turn off oven. Let meringues dry in oven, with door closed, for at least 1 hour. Remove from paper.
For berry sauce, thaw berries, if frozen. Do not drain. Place in a blender or food processor. Cover; blend or process nearly smooth. Strain berries through fine-mesh sieve; discard seeds (should have about 3/4 cup berries). Cover and chill.
To serve, scoop sorbet into meringue. Drizzle berry sauce on top. Sprinkle with sliced almonds. If desired, garnish with additional fresh berries. Serves 10.