Butter 9 x 13 baking pan.
Slice bread into cubes.
Top bread cubes with fresh blueberries. Set aside.
For custard:
Whisk together: eggs, milk, cinnamon, brown sugar, and vanilla until well mixed.
Pour custard over bread cubes & blueberries, coating all bread pieces.
Cover with plastic wrap and refrigerate overnight.
To bake:
Preheat oven to 350*
Prepare streusel topping: Mix the brown sugar, flour, and cinnamon together in a medium bowl. Cut in the cubed butter with a pastry blender or two forks. Sprinkle the topping over the soaked bread.
Bake for 45-50 minutes or until golden brown.
Optional toppings: butter, maple syrup, powdered sugar