Preheat oven to 350°F (175°C)

In a mixing bowl combine flour, baking soda and salt, whisk and set aside.

Using an electric mixer, or a stand mixer fitted with the paddle attachment, cream together butter and sugar until smooth.

Mix in egg, followed by egg yolk, vanilla and pudding mix. On a low speed, gradually add the dry ingredients, mixing until the dough comes together. Stir in sprinkles by hand.

Scoop dough using a small cookie scoop or tbsp and shape into balls. Drop onto parchment lined baking sheets, spacing cookies 2” apart. Top with sprinkles if desired, and bake for 9-10 minutes.

Allow cookies to cool on sheet for 5 minutes, before moving to a cooling rack.