Preheat the oven to 350°F (180°C), and line two baking sheets with parchment paper or silicone baking mats and set aside.
In a medium mixing bowl, whisk together the flour, baking soda, and salt. Set aside
In a separate bowl, cream together the butter, granulated sugar, and brown sugar until smooth and creamy. Add the egg and vanilla and mix on high speed until light and fluffy.
Add the flour mixture in 2-3 smaller additions, mixing well after each addition.
Divide the dough into 3 equal portions. Leave one portion as is, add the cocoa powder to one portion and mix, and finally add the freeze-dried strawberry powder and red food coloring if using to the last portion of dough and mix well.
Divide each flavor of dough into 18 equal pieces. Take one piece of each flavor of dough and roll into a small cylinder. Sandwich the dough together with vanilla in between chocolate and strawberry, then either roll into a ball or press into a 1.5-2 tablespoon cookie scoop for a more exact circle.
Roll each cookie in granulated sugar before placing on the prepared cookie sheets 2 inches apart. Bake in the preheated oven for 7-9 minutes, or until lightly golden around the edges. Allow to cool 5 minutes on the cookie sheet before transferring to a cooling rack to cool completely.
Notes
Change the look: instead of stacking the dough into a striped pattern, try centering the three colors in a circular pattern instead!
Instead of granulated sugar, you can roll the unbaked cookies in coarse sugar sprinkles.
Food coloring: Just the freeze-dried strawberries will give the dough a very pale pink color. You can add a drop or two of red or pink gel food coloring to achieve a more vivid color, but it's optional.
Don't overbake: The cookies are done when they are just lightly golden around the edges. This will ensure that the cookies are soft and chewy in the center.
To Store: Allow the cookies to cool completely, then store them in an airtight container for up to 3 days. These cookies can also be frozen for up to 3 months.