On a lightly floured surface, divide Shortcrust Dough into 12 equal portions and shape each portion into a ball. Gently press a dough ball into the bottom and up the sides of each of 12 (2½-inch) fluted tartlet pans, making sure bottom and sides are approximately ⅛ inch thick and trimming any excess. Place tartlet pans on a rimmed baking sheet, and refrigerate until firm, approximately 20 minutes.
Preheat oven to 350°F.
In a medium bowl and using a small rubber spatula, stir together butter and sugar until smooth. Stir in egg, almond extract, and salt until combined. Stir in almond flour.
Into each cold prepared tartlet pan, place 1 teaspoon strawberry jam. Divide almond mixture among tartlet pans, approximately 1 tablespoon each. Using a knife or a small spatula, spread almond mixture in a smooth layer to cover jam layer.
Bake tartlets until crusts are golden and filling is golden and set, 15 to 18 minutes. Let cool completely in pans.
In a small bowl, whisk together confectioners’ sugar and 1 tablespoon water until smooth, adding up to an additional 1 tablespoon water, 1 teaspoon at a time, until glaze is thick but fluid.
In a separate small bowl, stir together 2 tablespoons glaze and enough green food coloring to achieve desired green hue.
Spoon approximately 1 teaspoon plain glaze onto each tartlet, spreading gently to cover filling completely.
Transfer green glaze to a piping bag. Cut a ⅛-inch opening in tip of piping bag. Referring to step-by-step photographs and working with one tartlet at a time, pipe green glaze in a graduated zigzag pattern, making one end thinner than the other. Starting at tapered end, drag a wooden pick through the glaze to create the fern design. Place tartlets in an airtight container, refrigerate, and serve within 3 days. Serve cold or at room temperature.
Recipe by TeaTime Magazine at https://teatimemagazine.com/fern-cakes/