makes 1 dozen; adapted from Blue Bottle Coffee blog, September 14, 2017
Crush saffron threads with a small mortar and pestle until powdery.
Add milk, vanilla bean (if using), and saffron to a small saucepan and heat over low heat. Remove from heat, cover, and let steep for 10 minutes. After, remove vanilla bean, scrape seeds with a knife and add back to the milk, discarding the pod.
Cream butter and sugar for about 5 minutes, until light and fluffy.
Add egg, vanilla extract (if using), milk-saffron and mix until combined. Add flour, baking soda, and salt; mix until combined. Chill dough in refrigerator for 3 hours minimum or up to 5 days.
Preheat oven to 375°F. Using a 2-tablespoon-scoop, scoop dough balls and place 8 per half-sheet pan. Bake 14–16 minutes until beginning to turn golden brown at edges.