In a large mixing bowl, beat together butter, sugars, and salt with a mixer at medium-high speed until thick and creamy, approximately 2 minutes. Add egg, vanilla extract, and almond extract, beating until combined. Using an offset spatula, fold in flour until incorporated. (If necessary, use hands to bring dough together.)
Turn out dough onto a lightly floured surface, and divide in half. Shape each dough half into a disk, and wrap in plastic wrap. Refrigerate for at least 60 minutes.
Preheat oven to 400°. Line several rimmed baking sheets with parchment paper.
Working with one dough half at a time, turn out dough onto a lightly floured surface. Using a rolling pin, roll out dough to a ⅛-inch thickness. Lightly flour top of dough. Lightly flour an embossed rolling pin. Using embossed rolling pin, roll pin over dough once to imprint pattern. Using a 1¾-inch fluted square cutter, cut 30 cookies from dough. Using a thin-edge metal spatula, carefully transfer cookies to prepared baking sheets. Repeat with remaining dough half.
Bake until edges of cookies are barely lightly golden brown, approximately 7 minutes. Let cookies cool completely.
Place Custard Cream Filling in a piping bag fitted with a medium round tip (Wilton #12). Pipe Custard Cream Filling around edge of flat side of half of cookies, filling in outline. Cover with remaining cookies, patterned side up.
Using a dry, clean paint brush, brush edible dusting powder on tops of cookies, if desired. Serve immediately, or store cookies in an airtight container and refrigerate, up to 2 days. Let cookies come to room temperature before serving.
Notes
* We used a Uspacific embossing rolling pin, available from amazon.com.
** We used Kerry Vincent Pastels Berry Mist Edible Dusting Powder from CSA Sugar Art. Visit csasugartart.com for retailers.
Recipe by TeaTime Magazine at https://teatimemagazine.com/custard-cream-cookies-recipe/