Whisk egg whites in an electric mixer until soft peaks form.  Gradually add in both sugars and then vanilla and vinegar.  Increase speed and whip until mixture is free of sugar granules when rubbed between two fingers and the meringue forms stiff, glossy peaks.

Drizzle chocolate on top of meringue (do not mix in).  Spoon out mixture and drop onto a prepared baking sheet. Bake for 40–50 minutes at 275°F.