Step 1

Place 2 sticks unsalted butter in the bowl of a stand mixer (or large bowl if using an electric hand mixer). Place 1 large egg on the counter. Let both sit at room temperature until the butter is softened.

Step 2

Arrange 2 racks to divide the oven into thirds and heat the oven to 350°F. Line 2 baking sheets with parchment paper or silicone baking mats.

Step 3

Place 1 package freeze-dried strawberries in the bowl of a food processor fitted with the blade attachment (or in a blender) and process until the texture of fine flour, with no visible chunks of berries. Transfer to a medium bowl.

Step 4

Repeat the process with the 1 package freeze-dried raspberries and 1 package freeze-dried blueberries, placing them into separate bowls. (If your food processor or blender is unable to break the berries down completely, pass the powders through a fine-mesh sieve to remove any large pieces.)

Step 5

Add 1 cup of the granulated sugar and 1/3 cup packed light brown sugar to the butter. Mix on medium speed with the paddle attachment, scraping down the sides and bottom of the bowl halfway through, until smooth and fully combined, 2 to 3 minutes total.

Step 6

Turn the mixer off and add the egg and 1 tablespoon vanilla extract. Mix on medium speed until fluffy and lightened in color slightly, 2 to 3 minutes. Turn the mixer off and add 1 3/4 cups all-purpose flour, 3/4 teaspoon kosher salt, 1/2 teaspoon baking powder, and 1/4 teaspoon baking soda. Mix on low speed until a soft dough forms.

Step 7

Divide the dough into thirds (about 1 cup/240 grams per third) and add each portion to one of the bowls of freeze-dried berry powder. Mix the berry powders into the dough using a rubber spatula until completely combined. (Feel free to use clean hands to knead the berry powder into the dough if it’s giving you trouble.)

Step 8

Take 1 tablespoon of each dough and roll each into a rough 4-inch rope. Press the ropes together lengthwise so all three flavors are combined, twirl them into a rough spiral shape, then roll into a ball using the palm of your hands to create the marble pattern. (It’s okay to be a bit messy and imprecise.) Repeat with the remaining dough.

Step 9

Place the remaining 1/2 cup granulated sugar in a shallow, wide bowl and roll the dough balls in the sugar. Place 6 to 8 balls on each baking sheet, spacing them 3 inches apart.

Step 10

Bake both baking sheets at the same time, swapping the top sheet to the bottom rack and bottom sheet to the top midway through baking, until the tops of the cookies crack and the bottoms are just starting to brown, 13 to 15 minutes total. Immediately bang the baking sheets on the countertop to deflate the cookies slightly and then let them cool completely on the baking sheets.