1. Scrape vanilla beans into pure cane sugar and rub together to break up vanilla bean seeds into sugar. In a separate bowl, combine all dry ingredients. Cream butter and vanilla sugar together in mixer with paddle.
2. Add egg and continue to cream until full incorporated. Add milk and vanilla extract and continue creaming. Add dry ingredients to combine. Chill for at least 10 minutes.
3. Scoop 1 tablespoon rounds onto a sheet pan covered with a Silpat (or parchment sprayed with baking spray) and, with a damp palm, slightly press down on dough to create a bit of a flat disc shape. Sprinkle with plain sugar or make more vanilla sugar to use. Bake at 350° for 8-10 minutes.