Cream: In a bowl, thoroughly mix the butter, vanilla extract, and sugar until fluffed up. This is crucial for creating a light, airy texture in the cookies.
Add the Rest: First, blend in the egg to ensure smoothness in your mixture. Follow by adding the sourdough discard, then sift in the flour and baking powder.
Fold everything together gently to maintain the delicate structure of the batter. It should resemble soft vanilla ice cream in consistency.
Shape the Cookies: Using a tablespoon, scoop out approximately ¾ tablespoon of batter and place it on a baking mat.