Preheat oven to 350°F/175°C. Spray an 8-inch round cake pan or springform pan with vegetable cooking spray.
Combine vegan butter and sugar in a mixing bowl. Mix with a beater on medium speed for 1 to 2 minutes, until light and fluffy. Add flaxseed, cornstarch, and vanilla extract. Beat for another minute until combined and light.
In a bowl combine the flour, baking soda, baking powder, and salt. Stir to combine. Pour this into the bowl with the butter mixture. Mix on low speed until just combined.
Add 1 cup of chocolate chips to the batter. Add almond milk 1 tablespoon at a time, until you achieve a spreadable consistency. Press into the prepared pan.
Place the remaining chocolate chips on the top of the batter, pressing them in just a little. Bake for 20 to 25 minutes until edges of the crust are golden.
Optional: Decorate the edges of the cookie cake with chocolate frosting once it has cooled completely. This frosting tip from Amazon works great.