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1
Line two large baking sheets with parchment paper; set aside.
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2
In a large bowl, whisk together flour, cocoa, baking powder, baking soda, and salt; set aside.
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3
In the bowl of an electric mixer fitted with the paddle attachment, beat the butter and both sugars on medium speed until light and fluffy, 2 to 3 minutes.
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4
Add the egg and vanilla; beat to combine.
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5
With mixer on low speed, add flour mixture, and beat to combine, scraping down the sides of the bowl as needed.
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6
Turn out the dough onto a piece of plastic wrap, and divide in half.
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7
With floured hands, shape each piece into a flattened rectangle, wrap with plastic, and refrigerate until firm, about 30 minutes.
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8
Place one rectangle of dough on a lightly floured work surface.
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9
Roll out dough to a scant 1/8-inch thickness, stopping every so often to release the dough by running an offset spatula underneath.
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10
You should end up with a rectangle thats about 14 by 11 inches.
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11
Transfer dough to a prepared baking sheet, and freeze until very firm, about 30 minutes.
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12
Repeat with remaining dough.
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13
Preheat the oven to 350F.
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14
Place one rectangle of dough on a clean work surface.
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15
Working quickly, cut out rounds using a 2-inch cookie cutter.
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16
(If the dough begins to soften too much, return to the freezer for a few minutes.)
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17
Using a wide metal spatula, transfer rounds to parchment-lined baking sheets, about 1 1/2 inches apart.
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18
Gather together remaining scraps, reroll, and cut out more rounds.
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19
Freeze until firm, about 15 minutes.
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20
Repeat with the remaining rectangle of dough.
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21
Bake, rotating sheets halfway through, until the centers of the cookies feel firm when lightly pressed, 12 to 14 minutes.
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22
Transfer to a wire rack to cool completely.
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23
Using an offset spatula, spread 1 tablespoon desired filling onto the flat sides of half the cookies.
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24
Sandwich with remaining cookies, keeping the flat sides down.
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25
Unfilled cookies can be kept in an airtight container at room temperature for up to 1 week.
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26
Once filled, cookies are best eaten the day they are made, but they can be kept in an airtight container in the refrigerator for up to 3 days.
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27
In the bowl of an electric mixer fitted with the paddle attachment, combine all ingredients.
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28
Beat on medium-high speed until fluffy and light, 3 to 4 minutes.
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29
Use immediately or refrigerate in an airtight container for up to 3 days.
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30
Let soften at room temperature before using.
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31
Melt chocolates in a heatproof bowl set over (but not touching) simmering water, stirring occasionally.
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32
Add condensed milk, butter, and extract; stir to combine.
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33
Continue to stir over simmering water until all ingredients are smooth, 2 minutes.
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34
Remove from heat, and set aside to cool slightly.
