Preheat oven to 350 degrees. Prepare baking sheet with parchment paper.
Cream butter and sugar: In a large mixing bowl with a handheld electric mixer or standing mixer with paddle attachment, add in butter and sugar. Cream on medium speed until light and airy, about 3 minutes.
Meanwhile, mix flour and dry ingredients: In a medium mixing bowl, add in flour, salt, and baking soda.
Add in egg, egg yolks, and vanilla to the butter and sugar. Mix on medium speed until well combined, another minute.
Add in flour mixture in two batches. Mix on low speed, until just combined.
Remove 2/3 of the dough from the bowl. Feel free to eyeball. If you prefer to be more exact, I've weighed out the total dough (36 ounces for me based on this recipe) and then divided it into 3. However, I found that a perfect division didn't work because the strawberry and chocolate were slightly more dense upon adding in the chocolate/strawberries. So I'd reserve closer to 10 ounces dough reserved for vanilla and 12.5 ounces dough reserved for the strawberry and chocolate).
Make the pink dough: Take freeze dried strawberries or raspberries and place in a thick plastic bag. Using a rolling pin, pound and roll rolling pin over bag until strawberries/raspberries are a fine powder. Add powder and a teaspoon of water into the dough in the standing mixer and mix on low speed until evenly distributed. Set dough aside.
Make the chocolate dough: Take 1/3 of the reserved dough and place back in the standing mixer. Add in cocoa powder and a teaspoon of water and mix on low speed until evenly distributed. Set dough aside.
Assemble the dough: To make a single cookie, you'll use about a tablespoon of each dough. Once you have a tablespoon of each flavor, roll them together into a large smooth ball. This makes about 18 cookies. I prefer to do this in an assembly line. I'll divide each dough into a bunch of small balls (about a tablespoon or so) and then put the three doughs together. See above for a picture/video for help.Arrangement of Colors: You can either arrange the colors together in a line or more like a peace sign. See above for how each one looks.
Bake cookies: Place cookies on baking sheet- they'll spread a good deal, so give them space! I put 6 on a baking sheet to be safe. Bake until cookies are slightly puffed, about 11 minutes.