Beat softened butter and cream cheese for about 2 minutes at high speed in a large mixing bowl, using a hand held or stand mixer fitted with paddle attachment.
Add sugar and beat until light and fluffy, about 2 minutes on medium speed. Beat in egg till combined. Pour in both extracts and beat them in too. Scrape down the bottom and sides of mixing bowl as needed.
Sift all the dry ingredients (cake flour, baking powder and salt) over wet and mix on low speed till cookie dough forms. Roll into 18 balls and coat each into sprinkles. Place them on baking tray.
Cover and chill for around 1 ½-2 hours (up to 2 days) in fridge. If you choose to chill cookie dough for longer than 2 hours, you need to allow the dough to sit on counter for at least 30 minutes before you can form balls and roll them in sprinkles. It is because the dough would be quite hard when chilled for long.
This one is a thick dough, So, I generally roll the balls and coat them in non-pareils prior to chilling and bake them straight out of fridge after 2 hours. You can choose between whatever way is more convenient of chilling for you. When ready to bake, preheat your oven to 375 deg F and line 2 cookie trays with parchment paper or silicon mat and set it aside.
(If rolling the balls after chilling, form 18 balls out of the dough and roll them in sprinkles and coat all the balls.
Place the dough balls on pre-prepared cookie tray (2 inches apart) and bake for 9-10 minutes. Or till the cookies get golden on the bottom edges.
Allow to cool on baking sheets for 5 minutes before transferring to a wire rack to cool completely. Serve warm or store in an airtight container to enjoy later.