01 - Combine the butter and whole milk in a small saucepan over low heat. Once the butter has melted, stir in the granulated sugar and vanilla seeds (or vanilla sugar), mixing continuously until the sugar is fully dissolved.
02 - Remove the saucepan from heat and allow the butter-milk-sugar mixture to cool until just warm to the touch, 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 patches remain.
04 - Shape the dough into a ball, wrap it tightly in plastic wrap, and refrigerate for at least 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 - Lightly flour a clean work surface and roll the chilled dough out to an even thickness of about ⅛ inch (3 to 4 mm), rotating the dough as you roll to maintain a uniform thickness.
07 - Using a traditional rectangular fluted cookie cutter, cut out the biscuits and transfer each one carefully to the prepared baking sheet, leaving about ½ inch of space between them.
08 - Gently prick each biscuit several times with a fork to create the classic dot pattern. Bake on the center rack for 12 minutes, or until the edges turn a light golden brown.
09 - Transfer the biscuits to a wire cooling rack immediately and allow them to cool completely before serving. They will crisp up as they cool.