Lightly spray or grease a 9x13 inch baking dish.
Spread half the bread cubes in the prepared dish.
Top bread cubes with cream cheese cubes.
Sprinkle 2 cups of fresh blueberries over top of the cream cheese cubes.
Top blueberry layer with remaining bread cubes.
Meanwhile, in a large mixing bowl, whisk the eggs, milk, vanilla extract, and syrup.
Pour egg mixture over the bread cubes.
Cover, and refrigerate overnight.
Remove French Toast mixture from the refrigerator about 30 minutes before baking.
Preheat the oven to 350 degrees.
Cover with foil and bake 30 minutes.
Uncover, and continue baking 25 to 30 minutes longer.
The center should be firm and surface lightly browned.
In a medium saucepan over medium heat, mix the granulated sugar, cornstarch and water.
Bring ingredients to a boil.
Cook 4-6 minutes stirring constantly.
Add the remaining 1 ½ cups blueberries.
Reduce heat to low, and simmer approximately 10-15 minutes--until the blueberries burst.
Stir in butter to combine.
Pour blueberry syrup over top of the baked French toast.
Or serve slices of Blueberry French Toast and drizzle blueberry syrup over individual servings.