Chocolate Cookies:
Mix Dry Ingredients:
In a medium bowl, whisk together the flour, cocoa powder, baking soda, and salt. Set aside.
Cream Butter and Sugars:
In a large mixing bowl, beat together the softened butter, brown sugar, and white sugar until light and fluffy. Add the egg and vanilla extract, and beat until well combined.
Combine Wet and Dry Ingredients:
With the mixer on low speed, gradually beat the dry ingredients into the butter mixture, about ½ at a time. The dough will be sticky. Stir in the chocolate chips until evenly distributed.
Chill the Dough:
Cover the bowl with plastic wrap and refrigerate the dough for at least 3 hours or overnight.
Bake the Cookies:
Preheat the oven to 350°F (175°C) and line baking sheets with parchment paper or silicone baking mats.
Roll the chilled dough into balls about 1 to 1.5 tablespoons in size (a little smaller than a golf ball) and place them 2 inches apart on the prepared baking sheets.
Bake in the preheated oven for 8-10 minutes, or until the tops look set. Allow the cookies to cool on the baking sheets for 5 minutes before transferring them to a cooling rack to cool completely.
Raspberry Cream Cheese Frosting:
Prepare Raspberry Puree:
Add the raspberries to a blender or food processor and pulse until smooth.
Pour the puree through a metal sifter to remove the seeds, using the back of a spoon to push the puree through.
Reduce the Puree:
Transfer the seedless puree to a small saucepan over low heat. Gently bring it to a boil, stirring constantly. Continue to stir and cook until the mixture thickens to a jam-like consistency. You should end up with just a few tablespoons of thickened puree. Allow the puree to cool completely.
Make the Frosting:
In a large bowl, beat the softened butter until smooth. Add the cream cheese and beat until combined.
With the mixer on low speed, mix in 1 cup of powdered sugar and salt.
Add 1 tablespoon of the cooled raspberry puree and mix until fully incorporated.
Gradually add the remaining powdered sugar, about ½ cup at a time, adjusting the consistency by adding more raspberry puree as needed. The frosting should be thick and spreadable.
Assemble the Sandwiches:
Frost the Cookies:
Spread about 1 tablespoon of the raspberry cream cheese frosting on the bottom of one cookie, then sandwich with a second cookie on top. Repeat until all cookies are paired. You should have about 14 sandwich cookies in total.