In a medium to large sized bowl, add in flour, baking soda, and salt. Whisk well to combine, then set aside.

In a large bowl, or stand mixer (fitted with the paddle attachment), add the butter and both sugars and beat for 3 minutes, it should look light and fluffy, and expanded in size.

In a separate bowl, whisk together the eggs, yolk and vanilla, then add to the batter and beat on high for another 2 minutes, scraping at the edges periodically. Add in the flour mixture and mix on low until combined, scraping at the edges. Ensure it is well combined, but do not overmix. Add in the sprinkles, and fold with a spatula until well dispersed.

Prepare a baking sheet with parchment paper. Using your hands or a scoop, arrange cookies to be about 2 tbsp each. Place all the cookies onto the baking sheet (do not worry about arrangement yet), and place into the freezer for 30 minutes to rest (don’t skip, see above!)

Remove baking sheet from the freezer, and arrange cookies evenly onto 3 baking sheets fitted with parchment paper (I do 8-9 per sheet). Place into the oven and bake for 11-13 minutes.