These sandwich cookies are perfect for dunking into a tall glass of milk, or even a cappuccino.

Makes 20 sandwich cookies

PREP TIME: 30 minutes
CHILLING TIME: at least 3 hours, 30 minutes
COOKING TIME: 30 to 40 minutes

INSTRUCTIONS

COOKIES:

• 1 ¼ cups all-purpose flour
• ½ cup unsweetened cocoa powder
• 1 tsp baking soda
• Pinch of fine sea salt
• ¾ cup granulated sugar
• ¼ cup lightly packed golden yellow sugar
• 1 large egg
• 1 tsp vanilla extract
• ¾ cup unsalted butter, softened

FILLING:

• ½ cup unsalted butter, softened
• 1 ¾ cups icing sugar, sifted
• 1 tsp vanilla extract

INSTRUCTIONS

1. In a large bowl, whisk together the flour, cocoa powder, baking soda and salt. Set aside.
2. In a medium bowl and using an electric mixer, beat together both sugars, egg and vanilla extract. Add the butter and beat until the mixture is pale and fluffy, about 2 minutes.
3. Add the sugar mixture to the flour mixture and stir to combine. Refrigerate the dough, covered, for 30 minutes.
4. Scrape the dough out of the bowl onto a clean surface and form it into a log, about 10 inches long and 1 ¼ inches in diameter. Wrap it tightly in plastic wrap, then refrigerate for at least 3 hours, or overnight.
5. Preheat the oven to 350°F. Line two large baking sheets with parchment paper.
6. Unwrap the log, square it off and cut it into forty ¼-inch slices. Arrange the slices, 2 inches apart, on the prepared baking sheets.
7. Bake until dry to the touch, 6 to 8 minutes. (The cookies will still appear to be soft when done.)
8. Let the cookies cool for 5 minutes on the baking sheets, then remove to wire racks and let cool completely.
9. For the filling, in a small bowl and using an electric mixer on high speed, beat the butter until creamy, about 1 minute.
10. Add the icing sugar and vanilla extract. Beat on low speed for 1 minute. Increase the speed to high and beat until creamy and combined, 1 minute. (The filling will be thick.)
11. Spread half of the cookies with the filling. Top with the remaining cookies, squeezing them together gently. (The cookies can be stored in an airtight container at room temperature for up to 4 days.)

GET A HEAD START:

• Prepare the filling while the cookies are cooling or up to two days ahead.
• Refrigerate in an airtight container, then bring to room temperature before using.