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1
Preheat oven to 375F.
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2
Into a bowl, sift together flour, cocoa powder, baking soda, baking powder, and salt.
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3
In the bowl of an electric mixer fitted with the paddle attachment, cream sugar and butter until light and fluffy, about 2 minutes.
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4
Add egg; beat to combine.
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5
With mixer on low speed, gradually add flour mixture; continue beating until dough is well combined.
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6
Using a 1 1/4-inch ice cream scoop, drop dough onto parchment-lined baking sheets about 2 inches apart.
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7
Dip bottom of a glass in sugar; press to flatten cookies to about 1/8 inch thick.
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8
(You may need to carefully remove dough from glass with a thin metal spatula.)
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9
Transfer to oven and bake until cookies are firm, 10 to 12 minutes, rotating sheets halfway through.
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10
Transfer baking sheets to wire racks to cool completely.
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11
Place cream filling in a pastry bag fitted with a coupler, and pipe about 1 tablespoon filling onto the flat side of half the cookies.
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12
Place remaining cookies on top, and gently press on each to squeeze filling to edges.
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13
Filled cookies can be stored in airtight containers at room temperature up to 2 days.
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14
With an electric mixer, cream butter and shortening until well combined.
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15
On low speed, gradually add confectioners sugar and continue beating until light and fluffy, about 2 minutes.
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16
Add vanilla and beat to combine.
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17
Set aside at room temperature until ready to use.
