Step 1

Make the shortbread cookies: Sift the flour and icing sugar into a large bowl. Add the almond flour, cardamom, and salt and stir to combine.

Step 2

Cut the vegan butter into small cubes and add to the flour mixture. Using your hands, massage the butter into the flour mixture to form a shaggy and loosely combined dough. Add the agave and vanilla and mix together. If the dough is too dry, add 2 or 3 teaspoons of almond milk, a teaspoon at a time, and knead to form a shaggy dough.

Step 3

Turn the dough out onto a work surface. Using your hands, bring the dough together and knead to form a smooth ball. It is okay if there are a few dry spots. (Do not over-knead the dough or the cookies will be dense.) Wrap the dough in reusable wrap and chill in the refrigerator for 1 hour.

Step 4

Place the oven racks in the upper and lower thirds of the oven. Preheat the oven to 350°F (180°C). Line 2 baking sheets with parchment paper.

Step 5

Lightly dust the work surface with all-purpose flour. Using a rolling pin, roll out the dough into a rectangle or oval about ¼ inch thick. (Try to handle the dough as little as possible for a light and flaky texture when baked.) Using a 2½-inch round cookie cutter, cut out rounds and transfer to the prepared baking sheets, leaving a small space between each cookie. Re-roll the scraps and cut out more rounds. You should have at least 18 cookies.

Step 6

Bake the cookies until lightly golden on top, 8 to 10 minutes. For even baking, rotate the baking sheets front to back and top to bottom halfway through. Let the cookies cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.

Step 7

Sift the icing sugar into a small flat-bottomed bowl. Add 2 teaspoons of the almond milk and whisk together until smooth. If needed, add the remaining 1 teaspoon almond milk to thin the glaze.

Step 8

Turn the cookies upside down on a baking sheet. One at a time, dip the top of each cookie in the glaze to cover the surface. Place the cookies, iced side up, back on the baking sheet. While the icing is wet, garnish the cookies with the dried rose petals, if desired. Chill the cookies in the refrigerator until the icing has hardened, about 2 hours.