Preheat your oven to 350°F (175°C) and either line an 8x8-inch baking pan with parchment paper or lightly grease it.
In a tiny bowl, combine the flaxseed meal with water. Stir thoroughly and allow the mixture to rest for around 5 minutes until it thickens.
In a spacious mixing bowl, whip the softened vegan butter, brown sugar, and granulated sugar until the mixture is smooth and creamy.
Mix in the flax egg and vanilla extract until fully incorporated.
In another bowl, blend the flour, baking soda, and salt using a whisk until evenly combined.
Slowly incorporate the dry ingredients into the wet mixture, blending as you go. Stir until combined, but don’t overmix.
Gently fold in the vegan chocolate chips (and any nuts, if using).
Spread the dough evenly in the prepared baking pan and bake for 20-25 minutes, or until a toothpick inserted into the center comes out clean.
Allow the cookie bars to cool in the pan for 10 minutes, then transfer them to a wire rack to cool completely. Cut into 12 bars