Directions
<ol class="no-list-style"><li class="MethodStepper"><h4 class="step-title">Step 1</h4>Begin with the chocolate puff pastry. In a large bowl, sift together the flour and cocoa powder. Add the sugar and salt, then whisk to combine. Scatter the cold butter cubes over the dry ingredients and use your fingertips to flatten each cube. The butter should remain visible in flat sheets - this is crucial as these butter layers will create the flakiness in your pastry when baked.</li><li class="MethodStepper"><h4 class="step-title">Step 2</h4>Mix the ice-cold water with lemon juice, then drizzle over the flour-butter mixture. Use a knife to gently incorporate until a shaggy dough forms. Turn onto a lightly floured surface and knead just 4-5 times to bring it together - overworking will develop gluten and melt the butter, resulting in tough pastry. Shape into a rectangle, wrap in plastic, and refrigerate for 1 hour.</li><li class="MethodStepper"><h4 class="step-title">Step 3</h4>On a lightly floured surface, roll the dough into a rectangle about 20cm×40cm. Fold the bottom third up, then the top third down (like folding a letter). Turn 90 degrees so the open edge faces you. This is your first "turn." Roll out again and repeat the folding process. Wrap and chill for 30 minutes. Repeat this rolling and folding process two more times (for a total of 4 turns), chilling between each. This lamination process creates the delicate layers that make puff pastry exceptional.</li><li class="MethodStepper"><h4 class="step-title">Step 4</h4>While the dough chills, prepare the vanilla crème pâtissière. In a medium saucepan, heat the milk with the vanilla bean and seeds (or extract) until just before boiling. Meanwhile, in a bowl, whisk the egg yolks with sugar until pale, then whisk in the cornstarch until smooth. Gradually pour half the hot milk into the egg mixture while whisking constantly (this tempers the eggs and prevents scrambling).</li><li class="MethodStepper"><h4 class="step-title">Step 5</h4>Return this mixture to the remaining milk in the saucepan. Cook over medium heat, whisking continuously, until the cream thickens and begins to bubble. Continue cooking for 1-2 minutes more to cook out the cornstarch flavor. Remove from heat, discard the vanilla pod if used, and whisk in the butter until melted and incorporated. Pass through a fine sieve to ensure silky smoothness, then cover with plastic wrap directly touching the surface (to prevent a skin forming) and refrigerate until cool.</li><li class="MethodStepper"><h4 class="step-title">Step 6</h4>Preheat your oven to 200°C. Roll the chilled chocolate puff pastry to 2-3mm thickness. Cut into three equal rectangles slightly larger than your final dessert size. Dock the pastry sheets all over with a fork to prevent excessive puffing. Place between two silicone mats or parchment paper with a heavy baking sheet on top to keep them flat. Bake for 15-18 minutes until crisp but not burnt. Cool completely on wire racks.</li><li class="MethodStepper"><h4 class="step-title">Step 7</h4>To assemble, line your rectangular mold with acetate or a cake collar. Trim pastry sheets to fit perfectly inside the mold. Place one pastry sheet at the bottom, then spread half the chilled vanilla crème evenly on top. Add the second pastry layer, then the remaining crème, and finish with the third pastry sheet. Press gently to ensure layers are even. Refrigerate for at least 4 hours or overnight to set.</li><li class="MethodStepper"><h4 class="step-title">Step 8</h4>For the mirror glaze, bloom the gelatin by sprinkling it over 45ml cold water and let stand for 5 minutes. In a saucepan, combine the 150ml water, sugar, and condensed milk. Bring to a simmer, stirring until sugar dissolves. Remove from heat and add the bloomed gelatin, stirring until completely dissolved. Pour this mixture over the chopped chocolate and let stand for 2 minutes before stirring gently until smooth and glossy. Strain through a fine sieve to remove any bubbles or particles.</li><li class="MethodStepper"><h4 class="step-title">Step 9</h4>Allow the glaze to cool to 35-32°C - this is the optimal temperature for pouring (too hot and it will be too thin; too cool and it won't flow properly). Remove the mille-feuille from the refrigerator and unmold onto a wire rack set over a baking sheet to catch drips. Ensure the surface is clean and dry before glazing.</li><li class="MethodStepper"><h4 class="step-title">Step 10</h4>Pour the glaze in one continuous motion over the chilled mille-feuille, ensuring complete coverage. Allow excess to drip off for 5-10 minutes. Using a hot knife (dipped in hot water and wiped dry), trim edges for a clean finish. Carefully transfer to a serving platter and decorate with chocolate curls and gold leaf if desired. Refrigerate until ready to serve.</li><li class="MethodStepper"><h4 class="step-title">Step 11</h4>To serve, use a serrated knife dipped in hot water and wiped dry between cuts to slice cleanly through the layers. For the most beautiful presentation, clean the knife between each cut to maintain the mirror-like appearance of the glaze. The mille-feuille is best enjoyed the day it's glazed, when the pastry maintains its crispness against the creamy filling.</li></ol>