Preheat the oven to 350°F (180°C) and line two baking sheets with parchment paper.
In a small bowl, mix 1 tablespoon ground flax with 3 tablespoons water. Let it sit for 5 minutes to thicken.
1 tablespoon ground flax + 3 tablespoons water
In a large mixing bowl, cream together the cold vegan butter and both sugars for 2-4 minutes on medium-low speed until fluffy.
1/2 cup vegan butter, 1/2 cup organic brown sugar, 1/4 cup organic sugar
Add the thickened flax mixture and vanilla extract to the butter and sugar, mixing well.
1 teaspoon vanilla extract
In another bowl, combine the dry ingredients: flour, oats, cornstarch, baking soda, cinnamon, and salt.
1 1/4 cups all-purpose flour, 3/4 cup rolled oats, 1/2 teaspoon cornstarch, 1/2 teaspoon baking soda, 1/4 teaspoon cinnamon, 1/2 teaspoon salt
Gradually add the dry ingredients to the wet mixture, stirring until just combined—don't overmix.
Fold in the chocolate chips (and walnuts if using).
1 cup chocolate chunks or chocolate chips, Optional: 1/3 cup chopped walnuts
Scoop the dough into balls using a ¼ cup scoop and place them on the baking sheets.
Bake for 14-16 minutes or until the cookies are lightly golden on top.
Let the cookies cool on the baking sheet for a few minutes, then transfer them to a cooling rack to set.