Chocolate Sandwich Cookies with Chocolate Mascarpone Frosting

I made these sandwich cookies to use up some extra mascarpone frosting (see my Chocolate Espresso Cupcakes with Chocolate Mascarpone Frosting). I assembled the cookies right out of the oven and brought them over to a friend's house for dinner. The chocolate flavor of the cookies paired perfectly with the chocolate mascarpone frosting, but the cookies were a bit too crunchy-crispy and kind of smushed the frosting out the sides with each bite. When I got home I finished assembling the rest of the cookies and threw them in the fridge. The next day I tried them again and they were magically perfect! The cookies were tender and every bite of cookie and mascarpone frosting just melted in my mouth. They were awesome! The next time I make these, I might make them smaller, more like the size of oreos (the cookies in this picture are about 2.5 inches across). They would also make great ice-cream sandwiches... maybe I'll get to that next summer...

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RECIPE: Chocolate Sandwich Cookies with Chocolate Mascarpone Frosting
adapted from Martha Stewart's Cookies
makes about 2.5 dozen

INGREDIENTS:
Chocolate Mascarpone Frosting:
1/3 cup unsweetened cocoa powder
1 tablespoon instant espresso powder (optional)
1 1/2 cups heavy whipping cream, chilled (and divided)
1 1/3 cups sugar
2 8-ounce containers chilled mascarpone cheese

Cookies:
1 1/4 cups all-purpose flour
3/4 cup unsweetened cocoa powder
1 teaspoon baking soda
1/4 teaspoon baking powder
1/4 teaspoon salt
1.5 cups sugar, plus more for flattening cookies
10 tablespoons (1 1/4 sticks), room temperature
1 large egg, room temperature

DIRECTIONS:
Frosting (make ahead):
Sift cocoa powder into large bowl; add espresso powder. Bring 1 cup cream to boil in small saucepan. Slowly pour cream over cocoa mixture, whisking until cocoa is completely dissolved, about 1 minute. Add 1/2 cup cream and sugar; stir until sugar dissolves. Chill until cold, AT LEAST 2 hours. This can be made several days ahead; cover and keep chilled.

Add mascarpone to chilled cocoa mixture. Using an electric mixture, beat on low speed until blended and smooth. Increase speed to medium-high; beat until mixture is thick and medium-firm peaks form when beaters are lifted, about 2 minutes (do not overbeat or mixture will curdle).


Cookies:
Preheat oven to 375F. Line cookie sheets with parchment paper.
In a medium bowl, sift together flour, cocoa powder, baking soda, baking powder, and salt.

In the bowl of an electric mixer, beat the sugar and butter until light and fluffy, about 2 minutes. Add egg and beat until combined. With the mixer on low speed, gradually add flour mixture. Continue beating until dough is well combined.

Using a 1 1/4-inch ice cream scoop, or spoon of your choice, drop dough onto prepared baking sheets about 2 inches apart. Dip bottom of a glass in sugar; press to flatten cookies to about 1/8-inch thick. Carefully remove dough from bottom of glass if sticky.

Transfer to oven and bake until cookies are firm, 10-12 minutes, rotating sheets halfway through. Transfer baking sheets to wire racks to cool completely.

Spread frosting on bottom of one cookie, using about 1 tablespoon of frosting per cookie. Place another cookie on top. Gently press on each to squeeze filling to edges. Repeat with remaining cookies.

STORAGE:
Filled cookies should be refrigerated in air-tight containers. If you use a frosting that is fine to keep at room temperature, you may keep these cookies outside the refrigerator. For tender cookie sandwiches, store in the refrigerator.