Butter a 10-cup fluted tube pan or a 10-cup soufflé molds.
Preheat oven to 350 degrees.
In the mixing bowl of an electric mixer, combine the egg whites with cream of tartar and vinegar and beat at high speed until soft peaks form, about 1 minute. Continue beating, and gradually add the sugar, vanilla and cornstarch. Beat until very stiff, about 2 minutes. Spoon the meringue mixture into the prepared mold. Smooth the top of mold with a spatula. Place the mold in a baking pan containing hot water. Place the pan on the bottom rack of the oven and bake for 15 minutes.
The meringue will rise like a souffle above the top of the mold.
Remove pan from the oven. Allow the meringue to cool in the mold for 5 minutes. Unmold meringue on a deep platter surrounded by custard cream. Sprinkle floating island with toasted almonds, and decorate with sliced strawberries.