In a medium bowl whisk together eggs, milk, maple syrup, cinnamon and nutmeg.
Generously butter an 8"x8" pan. Spread half the bread cubes evenly in pan and dot with half of the cream cheese chunks. Sprinkle with 1/2 the blueberries. Repeat with remaining bread, cream cheese and blueberries. Pour egg mixture evenly over bread. Cover and refrigerate 8 hours or overnight.
Preheat oven to 375℉. Bake uncovered for 40-45 minutes until golden and set in the centre. Remove from oven and serve with balsamic blueberry sauce.
Balsamic Blueberry Sauce
In a medium sauce pan combine blueberries, sugar, and 4 tbsp of water. Cook over medium heat until simmering and sugar has dissolved, approximately 10 minutes. Stir together cornstarch and remaining 2 tbsp of water. Stir into blueberries and heat to a full simmer. Remove from heat and stir in vanilla and blueberry balsamic vinegar. Serve warm with french toast.
Balsamic Blueberry Sauce can be made a day ahead with the french toast and rewarmed for serving, or cooked while the Blueberry French Toast is baking. I made the french toast in muffin tins for presentation, however they were fussy to assemble and difficult to remove from tins. A single 8"x8" pan is recommended.