(You will not be preheating your oven until after the dough has chilled. When you do, you will preheat at 350℉). Set your vegan butter out to soften if it isn't already soft. It should be cool but soft - not warm and melty.
Stir in the white vinegar into the plant milk. Let it sit for a minute or two Then stir in the flax egg. Set aside while you assembling the other ingredients.
4 teaspoons ground flax, 4 Tablespoons plant milk, 1 teaspoons white vinegar
Please see the blog post to learn how to accurately measure the flour. Whisk the flour, cocoa powder, cornstarch, baking soda, baking powder, and salt together in a medium bowl. Set aside.
1¾ cups all purpose flour, 2½ Tablespoons unsweetened cocoa powder, 1 Tablespoon cornstarch, 1 teaspoon baking soda, 1 teaspoon baking powder, ¼ teaspoon salt
Add the softened vegan butter to a large bowl along with the brown sugar and granulated sugars. Beat until creamy, about 1 minute. Add in the flax egg/buttermilk mixture, agave nectar, and vanilla extract and continue mixing until all is incorporated. Once mixed, add the food coloring and beat until combined.
4 teaspoons ground flax, 4 Tablespoons plant milk, ½ cup vegan butter, ¾ cup brown sugar, ½ cup granulated sugar, 2 Tablespoons agave nectar, 2 teaspoons pure vanilla extract, 1/2 teaspoon gel red food coloring, 1 teaspoons white vinegar
Add in half of the flour mixture and mix until mostly incorporated. Add the rest of the dry ingredients and mix until a soft dough is formed. The dough will be sticky and soft at this point.
Cover and chill the dough in the refrigerator for at least 1 hour.
Preheat oven to 350°F. Line two large baking sheets with parchment paper or silicone baking mats. Set aside.
I use a cookie scoop to portion out small dough balls. If you don't have a cookie scoop then portion out about one-and-a-half tablespoons at a time. Roll into balls with your hands and place the balls onto the parchment lined baking sheet. Leave room for spreading. I can get 12 cookies on my large cookie sheet. Refrigerate the remaining dough while the first batch is baking and repeat.
Bake for 10-12 minutes until the cookies are slightly browned on the edges (which will be really hard to see) and are not jiggly when you move the baking sheet around.
Cool cookies on the baking sheet for 10 minutes before transferring to a parchment-lined wire rack to cool completely.
While the cookies are cooling, sprinkle some powdered sugar on top. Use a sieve/mesh to make it even and pretty. See blog post for photos.