Line two cookie sheets with parchment paper. Set aside.
Measure our your flour using the spoon and sweep method (spoon fluffed flour into your measuring cup and use a knife to "sweep" it level with the top of the measuring cup) or measure by weight.
In a large bowl, whisk together the flour, dry pudding mix, and baking soda. Set aside.
Using an electric mixer and the paddle attachment, beat the softened butter and sugar on medium speed for 2 minutes. The dough for these cookies is thick so a stand mixer works best here.
Next add the egg and vanilla and beat until well combined, scraping down the sides if needed.
Add the dry ingredients, 1 cup at a time, to the wet ingredients in the mixer until just combined. The dough will be very thick.
Fold in the sprinkles with a wooden spoon or baking spatula.
Using a large cookie scoop, scoop dough into 3 tablespoon scoops and place onto a parchment lined cookie sheet. Roll each cookie into a ball. For optional burst of sprinkles on top, place ¼ cup or so of sprinkles onto a plate and press each cookie dough ball into the sprinkles so there's extra on top.
Place in the freezer for about 20 minutes to firm up the dough a litte bit. I find the cookies spread less with a little chill on them so I never skip this step.
Ready to bake? When the cookies are almost done chilling, preheat oven to 350°F.
Space cookies 2-3 inches apart and bake on the (un-chilled) parchment paper lined cookie sheet on the center rack of the oven. This can be done in two batches (baking one after the other) or follow my lead and make some now and freeze the rest of the dough for later!
Bake for 12-13 minutes or until the edges of the cookies just start to turn a very light brown and barely start to crackle on top. Bake time will vary slightly based on cookie size. I like to make mine with a large scoop that yields 3 TBSP of dough per cookie. Smaller cookies will bake up a little faster so adjust as needed.
Once they're ready, carefully remove from oven and allow them to set-up on the cookie sheet for 3 minutes. Then transfer to a wire cooling rack to cool completely. Enjoy!
Fully cooled cookies can be stored in an airtight plastic container for a few days. See notes for freezer instructions.
Notes
Making these cookies in advance? You can leave them in the freezer until compoltely frozen and transfer to a baggie/container for easy grab and bake cookies whenever you want! You can also refrigerate the dough overnight to bake the following day. Both methods work great. For frozen cookie dough, I like to add an additional 30-60 seconds to the bake time to get them nice and crisp on the edges and soft in the center.Nutrition Facts below are estimated per cookie using an online recipe nutrition calculator. Adjust as needed and enjoy!