In a large bowl, whisk together the flour, baking powder and salt, then set aside.
In a stand mixer fitted with the paddle attachment, cream the butter, sugar, and vanilla for 2 minutes on medium speed, until fluffy and pale in color. Reduce the speed to low and add the egg yolks one at a time, waiting until the first one has been fully incorporated before adding the second. Then gradually add the flour mixture, one cup at a time, until it’s all fully combined.
If you'd like to use a cookie scoop, use a small cookie scoop to scoop out 20 balls of dough. Pour the sprinkles into a bowl, and bounce the balls of dough into the sprinkles to help them stick. Evenly space out on a large baking sheet lined with parchment, then bake at 350° degrees for 22-26 minutes, until the cookies are lightly golden in color. Let cool for 10 minutes before serving
If you are using a cookie cutter, Divide your cookie dough into 4 equal sized portions of dough. And let them chill in the fridge for 15 minutes, then preheat the oven to 350 degrees.
Roll the chilled dough out to ¼ to ⅓ of an inch on a well floured surface.
Use your cookie cutter to cut out the cookies, then evenly space them on a cookie sheet lined with parchment paper. (You should be able to get about 4 cookies per ball of dough with a 4-inch cookie cutter).
Once you have your cookies on your cookie sheet, brush on the egg wash, add sprinkles on top and then bake for 9-10 minutes. Place your cookies on a cooling rack and let cool for 10 minutes before serving.