Preheat oven to 300°F. Line baking sheet(s) with parchment paper.

Sift or sieve the flour, custard powder, baking powder, and salt into a bowl. Set aside.

With mixer on low speed, add the dry ingredients to the creamed mixture and blend until well incorporated.

Form dough into small round balls (either 18 or 20 grams dough per ball make lovely sized cookies). Place balls on prepared baking sheet(s), spacing the balls about 1¾” apart. With tines of a fork dipped in custard powder, flatten each ball to apx. ¼“ thick.

Bake for approximately 15-17 minutes, turning the pan once halfway through the baking process. Don’t over-bake as cookies will become dry. Let cookies cool on baking sheet for apx. 8-10 minutes then transfer cookies to wire rack to cool completely before adding icing and assembling into sandwich cookies.

Place butter in bowl of stand mixer fitted with paddle attachment and beat at medium speed until creamy, stopping to scrape sides of bowl, if necessary. Blend in the almond and vanilla extracts. Reduce mixer speed to low and gradually add the sifted icing sugar, about ¼ cup at a time. Add the water (or milk or whipping cream), a teaspoon at a time as the icing sugar is being blended in. If tinting icing, add a very tiny amount of gel icing color of choice. Increase speed to medium-low to blend ingredients then increase speed to high and beat an additional minute to ensure ingredients are well combined and icing is smooth. Additional liquid may be required to make icing of desired spreading/piping consistency. If adding additional liquid, add by ½ teaspoon at a time. Icing should be of spreading/piping consistency but not “soupy”.

Using a cake decorating tip of choice and piping bag filled with the icing, pipe icing all around outer edge (in about 1/16” from edge) of the flat side of half the cookies. Pipe a dob of icing in center of cookie. Alternatively, the icing can be applied using a knife or offset metal spatula. Top each iced cookie with a plain cookie, flat side toward icing. Press very gently to adhere cookie to icing. Cookies are now ready for serving. Cookies may be refrigerated in tightly sealed container for up to 3 days prior to serving or, for longer storage, freeze in airtight freezer-safe container. Cookies are best served at room temperature. Serve plain or dust with icing sugar at time serving.