• Preheat oven to 350°F (180°C). Line a large cookie sheet with parchment paper and oil the paper with cooking oil spray. Set it aside.
• In a mixing bowl or the bowl of a stand mixer, add egg and brown sugar until well combined.
• Using a hand whisk or the stand mixer's whisk attachment, beat on low speed until well combined - it takes 30 seconds.
• Add the natural peanut butter and baking soda. Switch to the paddle attachment if using a stand mixer, or use a rubber spatula to stir peanut butter into the egg mixture. It should come together into a cookie dough ball.
• Form 12 cookie dough balls of about 1 inch. Roll each ball into brown sugar (optional), then place them onto the prepared cookie sheet leaving half a thumb of space between each.
• Use the back of a fork to lightly press the cookie dough balls twice, in opposite directions, to form a crisscross shape on top of the balls.
• Bake in the center rack for 10-15 minutes until golden brown on the sides.
• Cool the peanut butter cookies for about 10 minutes on the cookie rack.
• Slide a spatula under each cookies to transfer to a cooling rack. They firm up as they cool down and reach room temperature.

Storage

• Store the cookies in a cookie jar for up to 1 week in the fridge. Freeze in zip-lock bags for up to 1 month.