Preheat oven to 325 degrees F. Line a baking sheet with parchment paper and set aside.

In a large, spotlessly clean bowl, beat egg whites on high speed for 3 - 4 minutes, until soft peaks form. Sprinkle in the cream of tartar and beat for 1 minute more.

Meanwhile, in a small bowl, use a fork to combine sugar, coffee, and cornstarch.

With beater still on high, slowly add sugar mixture, beating until the meringue is stiff, pliant, and has a nice sheen – for 4 - 5 minutes more. Finally, fold in the cocoa, followed by the balsamic.

Spoon onto prepared baking sheet and spread into an 8 - 10-inch circle, creating a few peaks and valleys as you do.

Gently slide pavlova into the oven, turn heat down to 300 degrees F, and bake for 45 - 50 minutes, or until the edges are the faintest golden, and the top is set but still has some spring. Turn off the heat, leave the oven door slightly ajar, and allow the pavlova to cool completely inside the oven. The cooked pavlova will keep well in an airtight container at room temperature for up to 3 days.

To serve, toss the fruit with 1 tablespoon sugar. Beat the cream to soft peaks, folding in 1 teaspoon of sugar right at the end. Pile the pavlova with whipped cream and top with berries. Slice, and serve immediately.