In a large saucepan, combine the sugar and cornstarch. Stir in the water until smooth. Add the blueberries. On medium heat, bring the mixture to a boil and continue to stir for about 2-4 minutes until the mixture has thickened. Remove from the heat, and cover with foil to keep warm.
For the pancakes:
In a large bowl combine the flour, sugar, baking powder and salt.
In a small bowl, combine the eggs, milk, sour cream, and butter. Stir into the dry ingredients until it is just moistened. Fold in the blueberries.
On a greased griddle over medium low heat, add 1/4 cup of the batter to the center. When small bubbles appear at the surface, flip the pancake and cook the other side until golden brown. Serve with blueberry topping
*If using frozen blueberries, do not allow to thaw to avoid discoloring the batter.