Preheat oven to 325 degrees and line 2 cookie sheets with parchment paper.

In a small bowl whisk together flour, baking soda, cream of tartar and salt.

In a stand mixer, fitted with the paddle attachment, cream butter and sugar together on medium speed until light and fluffy.

Add egg yolks and vanilla, mix well.

Turn speed down to low and slowly add flour mixture. Mix until just combined. (Do not overmix.) Remove bowl from stand and fold in sprinkles.

Using a one-ounce cookie scoop, scoop 12 balls of cookies onto each cookie sheet.

Bake one sheet at a time on the middle rack for 10-12 minutes.

Let cool on sheet for 5 minutes before transferring them to a cooling rack.