01 - In a small saucepan over low heat, gently melt the butter with the whole milk. Add the granulated sugar and vanilla seeds scraped from the bean, stirring continuously until the sugar has fully dissolved and the mixture is smooth.
02 - Remove the saucepan from heat and allow the butter-milk-sugar 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 mixing bowl. Stir with a wooden spoon or spatula until a smooth, homogeneous dough forms and no dry pockets of flour remain.
04 - Shape the dough into a ball, wrap it tightly in plastic wrap, and refrigerate for 1 hour to firm up the butter and make the dough easier to roll.
05 - Preheat the oven to 350°F using conventional (static) bake mode. Line a baking sheet with parchment paper and set aside.
06 - On a lightly floured work surface, roll the chilled dough out to an even thickness of approximately ⅛ inch (3 to 4 mm), using a rolling pin.
07 - Using a traditional fluted rectangular cookie cutter, cut out as many biscuits as possible from the rolled dough. Re-roll scraps and repeat until all the dough is used.
08 - Place the cut biscuits onto the parchment-lined baking sheet, leaving a small gap between each. Gently prick each biscuit several times with a fork to create the classic petit beurre pattern and prevent puffing.
09 - Bake on the center rack for 12 minutes, or until the edges and tops are a light golden brown. Rotate the tray halfway through for even browning.
10 - Transfer the biscuits to a wire cooling rack and let them cool completely before serving. This ensures they crisp up properly and develop their signature snap.