Grease 13 x 9 baking pan. Place half the bread cubes evenly in prepared pan.
Scatter cream cheese cubes over bread and sprinkle with 2 cups blueberries. Arrange remaining bread cubes over blueberries.
Make the custard: In a large bowl combine eggs, maple syrup, and milk. Whisk to blend. Pour evenly over the bread, blueberry, cream cheese mixture in the casserole pan.
Cover with foil and chill overnight.
To Bake: Preheat oven to 375 degrees. Bake, covered with foil, in middle of oven 30 minutes. Remove foil and continue baking 30 minutes longer. Or until puffed and golden brown.
Remove from oven and let set about 10 minutes before serving.
To Make Syrup: Meanwhile, in a small saucepan, combine sugar, cornstarch, and water over medium high heat. Cook stirring occasionally, 5 minutes or until thickened.
Stir in 1 cup blueberries and simmer, stirring occasionally, 10 minutes or until most berries burst. Add butter and lemon juice or zest (if using) and stir until butter is melted. You may prepare this up to 1 day in advance, refrigerate and gently reheat. Transfer to serving bowl.
Plate French Toast on individual serving plates and offer with both blueberry and maple syrups. Serving this with bacon and sausage makes a complimentary meal.