Preheat your oven to 350°F. Line a baking sheet with parchment and set aside.
In a medium bowl, measure out your flour, salt, baking powder and baking soda. Whisk together and set aside.
In a large bowl or the bowl of your stand mixer with paddle attached, cream together your butter and sugars on medium for 2-4 minutes until smooth.
Add in your egg, egg yolk and vanilla, mix on medium until incorporated well. Make sure to scrape down the sides and bottom of the bowl if using a stand mixer.
Add your dry ingredients and mix on low until just combined. This will most likely take 30 seconds or less.
Add in your sprinkles, and stir into the dough using a rubber spatula.
Using a 2 tbsp cookie scoop, scoop dough onto baking sheet, leaving a few inches on each side.
Bake for 10 minutes on the center rack of your oven. The edges will be lightly golden but cookies will still be soft in the center. Carefully transfer them to a wire cooling rack after they come out of the oven.
Store cookies in an airtight container for 3-5 days. Enjoy!
