These Chocolate-Pistachio Sandwich Cookies have light and smooth buttercream, with a lovely pale green color and a vibrant pistachio taste. Scoff all you want, but it’s exactly what these cookies needed.
In a small bowl, sift together the flour and baking powder and set aside for a moment. Cover two baking sheets with parchment paper.
Combine 10 oz of the chopped chocolate and the butter in a medium microwave-safe bowl. Microwave in 30-second increments until melted, stirring after every 30 seconds to prevent overheating. Stop heating when there are still a few bits of unmelted chocolate remaining, and continue to stir the chocolate until the residual heat melts the chocolate pieces. Set aside to cool for a few moments.
In a large mixing bowl, combine the eggs, sugar, vanilla, and salt. Beat with a whisk attachment on medium-high speed for 8-10 minutes until the mixture is pale yellow, fluffy, and voluminous. Add the melted chocolate and flour mixtures, and mix on low until almost combined. Stop when just a few streaks of flour remain, and add the remaining chopped chocolate and the pistachios. Stir until everything’s well-combined.
Set aside the dough at room temperature for at least 10-15 minutes, to give it a chance to firm up a little. If you refrigerate the dough at this point, it will become very hard, and will need to sit at room temperature to soften before using it. Preheat the oven to 350 degrees F. Scoop the dough by tablespoons onto the prepared baking sheets. You should get about 24-28 cookies. Bake the cookies for 10 minutes, until they’re puffed and crackly on top, but still soft in the middle. Let them cool completely on the trays before removing them.
To Make the Frosting:
Sift the dry pudding mix into a large mixing bowl—some brands (like Jell-O) include little bits of nuts, so they need to be sifted out unless you want nuts in your frosting. Add the milk to the pudding mix and whisk briefly, then let it sit for 5 minutes to absorb the milk and reduce the graininess of the sugar in the mix.
After 5 minutes, add the butter, powdered sugar, vanilla, salt, and almond extract to the mixing bowl. Mix everything together with a paddle attachment on low speed, until the powdered sugar is absorbed. Raise the speed the medium-high and beat until the frosting is light and fluffy. Adjust the texture by adding more powdered sugar if it is too runny, or more milk if it is too stiff.
To assemble the cookies, spread a generous layer of frosting on the bottom of one cookie, and press the bottom of another cookie on top. Press down until the frosting comes all the way out to the edges. Immediately roll the edges in some chopped pistachios, and repeat until all sandwich cookies are assembled.
Store in an airtight container at room temperature for up to 3 days. (They will last longer, but the cookies will start to get hard and stale.)