Make the pastry cream

• Start by bringing the milk and vanilla bean paste to a gentle simmer in a saucepan over medium heat, removing it the moment small bubbles appear.
• In a separate heat-proof bowl, whisk the egg yolks, sugar, and cornstarch until the mixture turns a pale, creamy yellow.
• Gradually stream about a quarter-cup of the hot milk into the yolk mixture while whisking vigorously; this tempering process ensures the eggs don't scramble.
• Return the entire mixture to the saucepan over low heat, whisking constantly as it thickens into a dense custard.
• To ensure the cornstarch is fully activated for a stable, pipeable set, allow the cream to bubble gently for exactly one minute before removing it from the heat.
• Whisk in the cold butter until the surface is glossy and silk-like, then transfer to a bowl and press plastic wrap directly onto the surface of the cream.
• Chill for at least three hours to allow the molecular structure to firm up.

Make the cookie dough

• Preheat your oven to 180°C (350°F) and prepare a parchment-lined baking sheet.
• Using an electric mixer, cream the room-temperature butter and sugar until the texture is light and aerated.
• Incorporate the egg and yolk on a low speed until the mixture is fully emulsified and smooth.
• Sift the flour and baking powder into the wet ingredients, mixing only until the last streaks of white disappear.
• Avoid over-developing the gluten, as this will cause the cookies to become tough rather than chewy.
• Roll 1.5-tablespoon portions into smooth, uniform spheres and space them evenly on the tray.
• Bake for 9 to 11 minutes; the goal is a cookie with set, golden edges and a center that remains pale and soft.
• Allow the cookies to stabilize on the hot tray for five minutes before moving them to a wire rack to reach room temperature.
• Once the cookies and cream are both completely cold, transfer the custard to a piping bag fitted with a large round tip.
• Pipe a thick, centered mound onto each cookie, leaving a small border to showcase the buttery base.
• Dust the top of the cream with an even layer of granulated sugar, ensuring full coverage to protect the custard from the flame.
• Hold the kitchen torch approximately two inches away and move it in rapid, circular motions until the sugar liquefies into a rich amber caramel.
• For a professional "shatter," apply a second light dusting of sugar once the first layer hardens and torch a second time.
• Serve within 30 minutes to maintain the perfect contrast between the brittle sugar shell and the silky cream.