Set aside 1/2 cup of the corn kernels. In a food processor or blender, combine the remaining 1 cup corn kernels with the egg substitute, yogurt, flour, walnuts, baking powder, baking soda, salt and pepper. Process for 30-60 seconds, until the batter is blended and smooth, stopping once or twice to scrape down the sides of the container. Transfer the mixture to a medium bowl and stir in the reserved corn.
Spray a large skillet, preferably nonstick, with nonstick cooking spray and place over medium heat.
When the skillet is hot (the batter should sizzle quietly as it hits the pan), make corncakes, cooking them just like pancakes and using about 1/4 cup of batter per cake.
Cook 2-3 minutes on the first side, until tiny bubbles appear around the edges, then turn carefully and cook about 2 minutes on the other side, until golden. If necessary, spray the skillet with additional nonstick cooking spray for cooking the next batch.
Accompany the corncakes with salsa and fat-free sour cream, if desired.