Prepare the Cookie Crust Dough

1. In a large mixing bowl, combine the all-purpose flour, whole wheat flour, granulated sugar, and salt.
2. Stir the dry ingredients together until well blended. Next, add the solid coconut oil. 
3. Now, mix in the apple cider vinegar. Begin adding ice-cold water, one tablespoon at a time, gently stirring after each addition. Continue adding water until the dough starts to come together. 
4. Be careful not to overwork the dough, as this can cause the cookies to become tough.
5. Once the dough forms, shape it into a disc, wrap it in plastic wrap, and refrigerate it for at least 30 minutes.

Prepare the filling

1. In a medium-sized saucepan, combine the blueberries, granulated sugar, cornstarch, lemon juice, lemon zest, vanilla extract, and a pinch of salt.

2. Place the saucepan over medium heat and cook the mixture, stirring constantly, until the blueberries release their juices and the mixture thickens. This should take about 5–7 minutes.

Roll out the dough

1. After the dough has chilled, remove it from the refrigerator and let it sit at room temperature for about 5 minutes to make it easier to roll out.

2. Lightly flour a clean surface and use a rolling pin to roll out the dough to about 1/8-inch thickness.

Cut the dough

1. Use a 2–3 inch cookie cutter to cut out circles from the dough. Make sure you have an even number of circles, as each cookie requires a top and a bottom.

2. Place half of the dough circles on a baking sheet lined with parchment paper.

Assemble the cookies

1. Preheat your oven to 375°F (190°C). On each dough circle placed on the baking sheet, spoon about 1 teaspoon of the cooled blueberry filling onto the center.

2. Next, place a second dough circle on top of each filled bottom circle. Gently press the edges together to seal the cookies.

3. Use a fork to crimp the edges, ensuring a tight seal and giving the cookies a decorative edge.

4. Then, use a sharp knife to cut a small “X” on the top of each cookie to allow steam to escape during baking.

5. Or, I also like to make a two or three small holes and put some fresh blueberries on top as you can see in the picture.

Bake the cookies

1. Brush the tops of the cookies with non-dairy milk using a pastry brush. This step helps create a beautiful golden-brown crust.

2. Place the baking sheet in the preheated oven and bake the cookies for 18–20 minutes, or until the edges are golden and the tops are lightly browned.