Prepare the Puff Pastry:
Preheat the oven to 400°F (200°C). Lay each puff pastry sheet on a baking tray lined with parchment paper. Place another baking sheet on top to keep them flat and bake for 15-20 minutes or until golden and crisp. Let them cool on a wire rack.

Make the Custard:
In a medium saucepan, combine milk, cream, and vanilla. Heat gently until just before boiling. In a mixing bowl, whisk together egg yolks, sugar, and cornstarch until smooth. Pour a small amount of the hot milk mixture into the egg mixture to temper it, whisking constantly. Gradually add the egg mixture back into the saucepan, stirring continuously until it thickens. Remove from heat and let it cool to room temperature.

Assemble the Layers:
Place one baked puff pastry sheet on a serving tray. Spread half of the custard evenly over it. Add the second puff pastry sheet and spread the remaining custard. Top with the third pastry sheet.

Prepare the Pink Icing:
In a bowl, mix powdered sugar, jam, and a small amount of water until smooth. Drizzle over the top layer of puff pastry.

Chill and Serve:
Chill the dessert in the refrigerator for at least 1 hour for easier slicing. Slice the custard slice into squares or rectangles and serve.