Arrange 1/2 the bread cubes in a greased 9"x13" baking pan. Sprinkle cream cheese cubes and blueberries evenly over the bread. Top evenly with remaining bread cubes. Mix together eggs, syrup, milk (or cream) and vanilla in a large bowl. Pour over bread cubes and, using a spatula, press down lightly to ensure the bread absorbs the liquid. Cover pan with foil and let chill in refrigerator overnight. In the morning, bake, covered with foil, at 350F for 30 minutes. Remove foil and bake for an additional 30 minutes, or until fluffy and golden. Meanwhile, in a medium saucepan over medium heat, cook water, sugar and cornstarch until thickened. Stir in blueberries and simmer for 10 minutes. Add butter and stir until melted. Drizzle over servings of French toast.