Take a large bowl. Cream the butter and brown sugar in that bowl with a hand mixer or an electric mixer fitted with a paddle attachment on high speed until smooth. Incorporate the vanilla extract and fully blend.

If you're using a stand mixer, take the bowl off and sift the flour and baking powder into the butter mixture.

Put the bowl back on the stand mixer and thoroughly incorporate the dry ingredients with the butter mixture. The dough will be quite crumbly.

Add just enough milk to bring the dough together. Whisk the dough until it becomes soft.

Place the dough on a plastic wrapper. Tightly wrap and form into the desired log shape. 

For at least two hours and up to overnight, refrigerate.

Set the oven temperature to 350°F. Use silicone baking mats or parchment paper to line a cookie sheet.

Cut the log of dough into 1/4-inch thick pieces. Leave plenty of space around the cookies, as they will spread.

Bake for ten to fifteen minutes or until golden brown. Allow the cookies to rest on the baking sheet for 5 minutes before transferring them to a wire rack to cool.

Your delicious Bordeaux cookies are ready. Bon Appetit!