I only had one complaint about these cookies when purchased fresh from the bakery: They were too large -- about the size of an English Muffin! That actually makes them too sweet as they don't divide easily, so you're essentially eating three very sweet cookies in one. By making your own, you can select the size of your choosing.
Cookie1 1/2 cups plus 3 tbsp AP flour
3/4 cup sugar
3/4 cup plus 1 tbsp unsweetened cocoa powder
1/2 teaspoon baking soda
1 1/2 teaspoons salt
15 tablespoons unsalted butter, cut into 3/4-inch cubes, at room temperature
Filling1/2 cup heavy cream
8 ounces white chocolate, chopped
For the Filling: In a small pan, bring the cream to a boil. Remove from heat and add the chocolate. Let stand for 1 minute, then whisk to melt the chocolate until smooth. Transfer to a small bowl, and let stand for at least 6 hours to thicken up.
For the Cookies: In a large mixing bowl, combine the flour, sugar, cocoa, baking soda, and salt, and mix on low speed. With the mixer running, add the butter, a piece at a time. The mixture will be dry and sandy at first, but over 2 minutes, will form pebble-sized pieces that start to cling together. Stop the mixer and transfer the dough to your board.
Preheat oven to 350°F.
Separate dough into 2 pieces. Roll each piece of dough between 2 pieces of plastic wrap or parchment paper to 1/8" inch thick. Using a cookie cutter, cut into rounds. Scraps can be pieced together and rolled out again. Place 1/2" apart on baking sheets lined with Silpat liners or parchment paper.
Bake for 12-15 minutes, rotating halfway through baking. Remove and cool in the pan for 5 minutes, then transfer cookies to a cooling rack. Cool completely.
To Assemble: Lightly whip the white chocolate cream to aerate and fluff up. Transfer filling to a pastry bag fitted with a 1/4" plain tip. Pipe about 1 1/2 tsp in the center of half the cookies. Top with another cookie to sandwich. Gently press down until the cream comes to the edges.
Cookies can be stored in a container for up to 3 days. Loosely cover.