Preheat oven to 350 degrees. Lightly butter an 8 ich square baking dish.
Spread one side of each trimmed white bread slice with butter. Cut each slice into 4 squares. Arrange in prepared baking dish with buttered side of bread facing up. Sprinkle bread with blueberries and cinnamon.
In a saucepan over medium heat, heat milk and sugar until warmed through, but do not allow to boil. Stir until sugar dissolves.
Whisk together warm milk mixture with eggs and vanilla, being careful to temper eggs a bit before blending. Pour custard over the blueberries.
Set baking dish in a larger pan, and add enough hot water to produce a 1 inch deep bath. Bake 45-60 minutes, or until a knife blade inserted near the center comes out clean. Remove custard from water bath and cool 10 minutes before serving; or chill to serve later. Makes 6 servings. Enjoy!