Whisk the ground flax seed and water together in a small bowl. Let the mixture sit until it gets goopy.
Next, microwave the butter until just melted.
Mix the wet ingredients together
To a medium-sized mixing bowl, add the flax seed egg and brown sugar. Stir together until incorporated. You may have to use your hands, the mixture will be thick.
Now mix in the melted butter and vanilla extract. Once just combined, mix in the shredded coconut.
Add the dry ingredients
Now add the flour, baking soda, and salt. Once the dry ingredients are almost completely incorporated, add the chocolate chunks. Continue mixing until everything is just combined.
Bake the pizookie
Preheat the oven to 325 degrees. Spread the batter evenly into an oiled 9 inch circular metal pan.
Bake the pizookie for 35 minutes. It will be set on top and a toothpick inserted in the middle will come out mostly clean. Don’t overbake!
Cool, serve, enjoy
Let the pizookie cool in the pan for at least 30 minutes before slicing.