Preheat the oven to 350°F. Line a rimmed baking sheet or jelly-roll pan with parchment paper and set aside.

Separate the 6 large eggs. In a clean, dry mixing bowl, beat the egg whites while gradually adding 6 tablespoons sugar until stiff, glossy peaks form.

Gently fold the 6 egg yolks into the beaten whites until just combined.

Sift together 5 tablespoons potato starch and 1 tablespoon sifted cocoa. Fold the sifted potato starch and cocoa into the egg mixture until just incorporated.

Fold in 2 tablespoons oil gently until the batter is uniform. Pour the batter onto the prepared baking sheet and spread to an even layer.

Bake the cake for about 20 minutes, or until the top springs back lightly when touched and a toothpick in the center comes out clean.

While the cake bakes, lay a clean kitchen towel on the counter and sprinkle it with a light dusting of potato starch (from the "plus more for sprinkling").

When the cake is done, immediately invert the hot cake onto the prepared towel and carefully peel off the parchment paper.

Starting from one short edge, roll the cake and towel together into a tight jelly-roll. Set the rolled cake aside and let it cool completely while rolled.

Meanwhile, prepare the filling: beat 6 ounces whipped cream cheese with 3/4 cup sugar until smooth and well combined.

Melt 3 1/2 ounces milk chocolate in a double boiler or in short bursts in the microwave, stirring until smooth. Let the melted milk chocolate cool slightly (so it will not melt the cream cheese when applied).

Unroll the cooled cake carefully. Spread a thin, even layer of the melted milk chocolate over the cake, then spread the cream cheese mixture evenly on top of the chocolate. Re-roll the cake tightly without the towel.

Dissolve 1 teaspoon instant coffee granules in 1–2 teaspoons water. Melt 3 1/2 ounces white chocolate in a double boiler or microwave, then stir in the dissolved coffee until smooth to make the glaze.

Pour or spread the white chocolate coffee glaze evenly over the rolled cake. Place the glazed cake in the freezer until the glaze is set.

To serve, remove the cake from the freezer and let it defrost slightly (about 10–15 minutes) before slicing.