Mix butter and brown sugar together just until combined - do not cream it or over beat it. Add milk and vanilla, gently mix until combined.

In a separate bowl, whisk together remaining ingredients.

Add dry mix to butter and sugar, mix until combined, then knead lightly until smooth.

Wrap dough in plastic film, chill for 1 hour.

Preheat the oven to 350 F (180 C), line baking sheets with parchment paper.

Generously sprinkle clean work surface with corn starch, roll dough to ½" thick.

Cut into traditional rectangles, or use cookie cutters to cut out whatever shapes you’d like.

Place cookies 2" apart on prepared baking sheets.

Bake for about 15 minutes, or until lightly golden.

Allow cookies to cool on cookie sheets for at least 5 minutes before moving, cool completely before serving.