To prepare cookies: Whisk all-purpose flour, spelt flour, espresso powder, cinnamon, cardamom (or ginger or allspice) and salt in a medium bowl.

Beat 8 tablespoons butter, brown sugar and turbinado sugar in the bowl of a stand mixer fitted with the paddle attachment (or in a large bowl with a hand mixer on medium speed), scraping the sides as needed, until smooth and creamy, about 3 minutes. Add egg and beat for 1 minute. Beat in molasses and vanilla on low speed. Add the dry ingredients and beat on low speed just until the dough comes together. Transfer the dough to a clean work surface. Divide in half and pat each half into a disk.

Working with one disk at a time, place the dough between two sheets of parchment paper and roll to a thickness of 1/8 inch. Stack the rolled dough in parchment on a baking sheet and freeze for 1 hour (and up to 3 months) or refrigerate for at least 3 hours (and up to 3 days).

Preheat oven to 350°F. Line 2 baking sheets with parchment paper or silicone baking mats.

If the dough has been frozen, let stand at room temperature for 5 minutes. Working with one piece of dough at a time and using a 2- or 2-1/2-inch star-shaped cookie cutter, cut out as many cookies as you can. Place them about 1 inch apart on the prepared baking sheets. Gather the scraps and roll and cut the remaining dough.

Bake the cookies, one pan at a time, until golden and only just firm, 8 to 9 minutes. Let cool on the pan for 2 minutes, then transfer to a wire rack.

To prepare glaze: Whisk egg white in a medium bowl until frothy. Add confectioners' sugar and stir with a flexible spatula until incorporated. Stir in melted butter and mix until you have a smooth glaze that spreads easily, adding a drop or two of warm water if needed.

Using a small offset spatula or a butter knife, spread the glaze over each cookie. If you'd like to add some sprinkles, a little chocolate pearl or three, or anything else you fancy, do it while the glaze is fresh. Let the cookies dry at room temperature for 1 hour.