Step 1: Prepare the Flax Egg and Preheat Oven
First things first, make your flax egg. In a small bowl, whisk together 1 tablespoon of ground flaxseed meal and 2.5 tablespoons of water. Set it aside to gel for at least 5 minutes. While it’s gelling, preheat your oven to 350°F (175°C). Line two large baking sheets with parchment paper. This prevents the cookies from sticking and ensures even browning on the bottom.

Step 2: Cream the Fats and Sugars
In a large mixing bowl, combine the softened vegan butter, natural peanut butter, packed light brown sugar, and granulated white sugar. Using an electric hand mixer or a stand mixer fitted with the paddle attachment, beat the ingredients together on medium speed for about 2-3 minutes. The goal is to get the mixture light, fluffy, and pale in color. This process, known as creaming, incorporates tiny air pockets into the dough, which is fundamental for a light and tender cookie texture. If you don’t have an electric mixer, you can do this by hand with a whisk and some elbow grease, but it will take longer.

Step 3: Add the Wet Ingredients
Once the butter and sugars are creamed, add your now-gelled flax egg and the pure vanilla extract to the bowl. Beat again on medium speed for another minute until everything is fully incorporated and the mixture is smooth. Scrape down the sides and bottom of the bowl with a spatula to ensure everything is evenly mixed.

Step 4: Combine the Dry Ingredients
Add the all-purpose flour, baking soda, baking powder, and fine sea salt directly into the same bowl on top of the wet ingredients. Start mixing on the lowest possible speed (or mix by hand with a spatula) until the dry ingredients are just combined. Be very careful not to overmix at this stage. Overmixing develops the gluten in the flour, which will result in tough, dense, and rubbery cookies instead of soft and chewy ones. Stop mixing as soon as you no longer see streaks of flour. The dough will be soft and a little sticky.

Step 5: Chill the Dough (Highly Recommended)
This step is optional if you’re in a hurry, but highly recommended for the best results. Cover the bowl with plastic wrap and chill the dough in the refrigerator for at least 30 minutes, or up to 24 hours. Chilling the dough does two wonderful things:

1. It prevents spreading: The cold fat solidifies, meaning the cookies will spread less in the oven, resulting in thicker, chewier cookies.
2. It deepens the flavor: As the dough rests, the flour has more time to hydrate, and the flavors meld together, resulting in a more complex and intensely peanut-buttery taste.

Step 6: Scoop, Shape, and Press
Once the dough has chilled, use a medium cookie scoop (about 1.5 tablespoons) to portion out uniform balls of dough. Roll each portion between your hands to create a smooth ball and place them about 2-3 inches apart on the parchment-lined baking sheets. For the classic peanut butter cookie look, take a fork and gently press down on the top of each dough ball, then press again from the opposite direction to create a crisscross pattern. This not only looks beautiful but also helps to flatten the cookie slightly for more even baking. If the fork sticks to the dough, dip it in a little granulated sugar between presses.

Step 7: Bake to Golden Perfection
Bake the cookies in the preheated oven for 10-12 minutes. The exact time will depend on your oven. The cookies are done when the edges are set and golden brown, but the centers still look slightly soft and a little underbaked. Do not overbake them! They will continue to cook and firm up on the hot baking sheet after you take them out of the oven. This is the secret to a perfectly chewy center.

Step 8: Cool and Enjoy
Let the cookies cool on the baking sheet for 5-10 minutes. They will be very fragile right out of the oven, so this allows them to set. After 5-10 minutes, use a thin spatula to carefully transfer them to a wire rack to cool completely. The texture will be at its absolute best once they have cooled to room temperature.