Step 1

Preheat your oven to 350°F. Line rimmed baking sheets with unbleached parchment paper and set them aside.

Step 2

In a large bowl, place the flour, xanthan gum, baking powder, salt, granulated sugar and confectioners’ sugar and whisk to combine well.

Step 3

Add the butter, and mix to moisten the dry ingredients with the butter, until the mixture looks sandy, pressing down on the butter with the back of the mixing spoon.

Step 4

Add the egg and vanilla, and mix to combine, until the dry ingredients are all moistened with the wet.

Step 5

With clean, dry hands, knead the mixture together to form a cohesive dough. It will be thick and relatively stiff.

Step 6

Place the dough on a clean, flat surface, and roll it into a round a bit less than 1/3-inch thick, sprinkling very lightly with flour to prevent the rolling pin from sticking.

Step 7

Using a 2 1/2-inch round cookie cutter (or whatever shape you like), cut out shapes from the dough and place them about 1-inch apart on the prepared baking sheets.

Step 8

It can be helpful to remove the surrounding dough from the cutouts, and then peel the shapes off. Gather and reroll the scraps and repeat the process until you’ve used all the dough.

Step 9

Place the baking sheet in the center of the preheated oven and bake until the cookies are just set on top, 6 to 8 minutes, depending upon size and shape. The edges of some cookies may brown slightly.

Step 10

Remove them from the oven before there is any significant browning, and allow them to cool on the baking sheet until set before transferring them to a wire rack to cool completely.

Step 11

In the bowl of your stand mixer fitted with the paddle attachment, place the butter, milk and vanilla, and mix on medium speed until combined. Increase the mixer speed to high and mix until creamy.

Step 12

Add the salt, meringue powder and about 3 1/2 cups of confectioners’ sugar. Mix slowly until the sugar is incorporated. Turn the mixer up to high and beat until it becomes uniformly thick.

Step 13

Add the optional vanilla seeds and as much of the rest of the confectioners’ sugar as necessary to thicken the frosting, and beat to combine well.

Step 14

Once the cookies are completely cool, pipe or spoon a generous amount of frosting onto the top of each, and spread into an even layer with a wide knife or offset spatula. Scatter sprinkles, if desired.

Step 15

Allow the cookies to set at room temperature until the frosting hardens a bit. Store any leftovers in an airtight glass container at room temperature. Freeze any plain cookies for longer storage.