Cut bread into 1-in. cubes; place half in a greased 13x9-in. baking dish. Cut cream cheese into 1-in. cubes; place over bread. Top with blueberries and remaining bread cubes.
Whisk the eggs, milk and syrup in a large bowl. Pour over bread mixture. Cover and refrigerate for 8 hours or overnight.
Remove from the refrigerator 30 minutes before baking. Cover and bake at 350° for 30 minutes. Uncover; bake 25-30 minutes longer or until a knife inserted in center comes out clean.
Combine the sugar, water and cornstarch until smooth in a small saucepan. Bring to a boil over medium heat; cook and stir until thickened, 3 minutes. Stir in blueberries; bring to a boil. Reduce heat and simmer until berries burst, 8-10 minutes. Remove from heat; stir in butter. Serve with French toast.
