From 6 Bittersweets
From The Craft of Baking by Karen DeMasco and Mindy Fox via Leite's Culinaria
Supposedly makes about 2 dozen sandwich cookies
XIAOLU'S NOTES: Following the recipe, I got nearly 4 dozen sandwiches. So I'd recommend making larger balls (3/4 to 1-inch) or, if you like the look of these tiny bites, setting aside some extra time/patience to form the smaller balls! I've read that the filling is a winner, so I'm posting the original recipe below and plan to try it next time.
For the peanut butter cookies
1 3/4 cups unbleached all-purpose flour, plus more for rolling
1 teaspoon baking powder
1/2 teaspoon baking soda
1/2 teaspoon kosher salt
6 tablespoons unsalted butter, at room temperature
1/2 cup plus 1 tablespoon lightly packed dark brown sugar
3/4 cup plus 1 tablespoon confectioners’ sugar
1/2 cup creamy peanut butter
1/2 cup vegetable oil
1 1/2 teaspoons pure vanilla extract
1 large egg, room temperature
For the milk chocolate filling
6 ounces milk chocolate, roughly chopped
1/2 cup creamy peanut butter
1/4 cup powdered (confectioners') sugar
1/4 teaspoon kosher salt
3/4 cup heavy cream
Preheat the oven to 350 degrees F. Line two baking sheets with parchment paper.
In a large bowl, sift together the flour, baking powder, baking soda, and salt.
In the bowl of an electric mixer fitted with the paddle attachment, beat the butter, brown sugar, and confectioners’ sugar on medium-high speed until light and fluffy, about 2 minutes. Add the peanut butter and beat to combine, scraping down the sides of the bowl as needed. With the mixer on low speed, slowly add the oil, vanilla, and egg and beat until just combined, about 20 seconds. Add the flour mixture, beating just to combine.
Lightly flour the palms of your hands, and roll the dough into balls about 1/2 inch in diameter. Place them about 1 inch apart on the prepared baking sheets. Bake, rotating the sheets halfway through, until the cookies are golden brown on the edges, about 12 minutes.
Transfer the baking sheets to wire racks and let cool completely. (The peanut butter cookies can be stored, unfilled, in an airtight container at room temperature for up to 1 week.)
Combine the chocolate, peanut butter, confectioners’ sugar, and salt in a medium bowl. In a small saucepan, bring the cream to a boil. Remove the cream from the heat and pour it over the chocolate mixture. Stir with a spatula until the chocolate is completely melted.
Set the bowl in an ice bath, or chill it in the refrigerator, until the filling has cooled to room temperature and is thick enough to spread. Then use it immediately or transfer it to an airtight container and refrigerate it for up to 1 week (let it come to room temperature before using).
Using an offset spatula, spread 1 teaspoon of the milk chocolate filling [or ganache] over the flat sides of half of the cookies. Sandwich with the remaining cookies, flat sides together.
Once filled, the cookies are best eaten the same day, but they can be kept in an airtight container in the refrigerator for up to 3 days.