Preheat the oven to 355°F (180°C) with a convection setting. Roll out the puff pastry on a lightly floured surface and cut it into two even rectangles. Transfer the rectangles to a parchment-lined baking sheet and bake for about 30 minutes, or until deeply golden and crisp. Bake any leftover scraps separately—they will be used for garnish. Remove from the oven and let cool completely for 30 to 60 minutes. Once cooled, carefully slice each rectangle in half horizontally to create four layers.

In the bowl of a stand mixer fitted with the whisk attachment, beat the heavy cream, milk, pudding mix, and sugar until stiff peaks form.

Place one puff pastry layer on a serving platter. Spread a quarter of the cream mixture evenly over the pastry. Repeat the layering process, finishing with a layer of cream on top. Use an offset spatula to coat the sides of the cake with the remaining cream, smoothing it out for a clean finish.

Crumble the baked pastry scraps and sprinkle them over the top. Refrigerate for at least four hours to allow the cream to set. Before serving, dust generously with powdered sugar.