Step 2: In a small bowl, whisk together the flour, cornstarch, cocoa powder, baking powder, and salt. Set aside.

Step 3: Separate the eggs, placing whites in one large mixing bowl and yolks in another. Beat the egg whites on medium-high speed until they become foamy. Gradually add 1/2 cup of sugar while continuing to beat. Increase speed to high and beat until stiff peaks form. The peaks should stand straight up when you lift the beaters.

Step 4: In the second bowl, beat the egg yolks with the remaining 1/4 cup sugar and vanilla extract until the mixture becomes thick and pale yellow, about 3 minutes.

Step 5: On low speed, mix the flour mixture into the yolk mixture until just combined. Stir in one-quarter of the beaten egg whites to lighten the batter, then gently fold in the remaining whites using a rubber spatula. Be careful not to deflate the mixture.

Step 6: Spread the batter evenly into the prepared pan, smoothing the top with an offset spatula. Bake for 12 to 14 minutes, or until the top springs back when lightly pressed.

Step 7: Let the cake cool in the pan for 2 minutes. Meanwhile, dust a clean kitchen towel generously with powdered sugar. Loosen the edges of the cake with a knife, then invert it onto the prepared towel. Carefully peel off the parchment paper.

Step 8: Starting from a short end, roll the cake up in the towel. Place seam-side down on a wire rack and let cool completely, about 30 minutes.

Step 9: While the cake cools, remove the ice cream from the freezer and let it soften at room temperature until spreadable, about 15 to 20 minutes.

Step 10: Carefully unroll the cooled cake. Spread the softened ice cream evenly over the cake, leaving a small border around the edges.

Step 11: Sprinkle the chopped malted milk balls evenly over the ice cream, pressing them gently into the surface.

Step 12: Roll the cake back up without the towel, working gently but confidently. Wrap tightly in parchment paper, then wrap again in aluminum foil. Place seam-side down in the freezer and freeze overnight until completely firm.

Step 13: In a small saucepan, combine the heavy cream, chopped chocolate, and corn syrup. Heat over low heat, stirring constantly, until the chocolate melts completely and the mixture becomes smooth and glossy, about 1 to 2 minutes. Remove from heat and stir in the vanilla extract. Let the glaze cool to room temperature.

Step 14: Unwrap the frozen cake roll and trim both ends for a clean presentation. Place the cake on a wire rack set over a baking sheet or parchment paper to catch drips.

Step 15: Pour the cooled glaze along the top of the cake roll, using a spatula to spread it over the sides. The glaze will set quickly on the frozen cake. If desired, sprinkle additional crushed malted milk balls on top before the glaze sets completely.

Step 16: Return the glazed cake to the freezer uncovered for about 1 hour, or until the glaze is completely firm. Once set, you can wrap it for storage.