01 - Gently melt the butter with the whole milk in a small saucepan over low heat. Stir in the sugar and vanilla seeds until fully dissolved and the mixture is smooth.
02 - Remove from heat and allow the butter-milk mixture to cool slightly until lukewarm, then transfer it to a large mixing bowl.
03 - Add the all-purpose flour, baking powder, and fine sea salt to the bowl. Mix thoroughly until a smooth, homogeneous dough forms without any dry pockets.
04 - Shape the dough into a ball, wrap it tightly in plastic wrap, and refrigerate for at least 1 hour to firm up and develop texture.
05 - Preheat the oven to 350°F using conventional (static) heat mode. Position the rack in the center of the oven.
06 - On a lightly floured work surface, roll the chilled dough out to an even thickness of about ⅛ inch (3–4 mm), working quickly to keep the dough cool.
07 - Using a traditional fluted rectangular cookie cutter, cut out the petit beurre shapes from the rolled dough. Re-roll scraps once and continue cutting.
08 - Place the cut biscuits onto a baking sheet lined with parchment paper, leaving about ½ inch of space between each one.
09 - Lightly prick each biscuit several times with a fork to prevent puffing. Bake for 12 minutes or until the edges turn a light golden brown.
10 - Transfer the biscuits to a wire cooling rack and let them cool completely before serving. This ensures maximum crispness.