Preheat oven to 375º F. Lightly grease an 8" or 9" square pan at least 1.5" tall.
Mix ground flax seed with the water and set aside.
Add all the topping ingredients to a bowl and smash together with a fork until coarse crumbs form. Set aside.
Whisk together flour, baking powder, and salt in a medium bowl.
In another bowl, beat together the sugar, flax mixture, Earth Balance, and vanilla until creamy.
Alternatively beat in the flour mixture and the non-dairy milk to the creamed sugar mixture until combined. Gently stir in the blueberries.
Spread the batter evenly in your greased pan. Spread the topping crumbs evenly over the batter.
Bake 35-45 minutes at 375º F until a knife inserted in the center comes out clean. Ovens can vary greatly. If you want to be cautious, start checking it at 30 minutes. Let it cool for about 10 minutes before serving.