01 - Gently melt the butter with the whole milk in a saucepan over low heat. Add the sugar and vanilla, stirring continuously until fully dissolved.
02 - Remove from heat and allow the mixture to cool slightly, then transfer it to a large mixing bowl.
03 - Add the flour, baking powder, and salt to the bowl. Mix until a smooth, homogeneous dough forms.
04 - Shape the dough into a ball, wrap it tightly in plastic wrap, and refrigerate for 1 hour to firm up.
05 - Preheat the oven to 350°F using conventional (static) heat mode.
06 - On a lightly floured work surface, roll the dough out to an even thickness of about ⅛ inch.
07 - Using a traditional fluted rectangular cookie cutter, cut out the petit beurre shapes from the rolled dough.
08 - Place the cut biscuits onto a baking sheet lined with parchment paper, spacing them slightly apart.
09 - Prick each biscuit lightly with a fork to prevent puffing. Bake for 12 minutes until golden brown.
10 - Transfer the biscuits to a wire cooling rack and let them cool completely before serving.