Lightly butter a 13x9-inch baking dish.
Diagonally cut bread into 1-inch slices and place slices into prepared baking dish.
In a medium bowl, combine eggs, sugar, and vanilla extract; add milk and stir until blended. Pour mixture over bread slices, turning slices to make sure they are well coated. Cover and refrigerate at least 6 hours or overnight.
Preheat oven to 375 degrees F. Position oven rack in center of the oven.
Remove bread mixture from refrigerator and spread blueberries over the top of the bread.
In a small bowl, combine flour, brown sugar, and cinnamon. With a pastry blender or two knives, cut in butter until particles are the size of small peas. Spread mixture over the top of the blueberries.
Bake approximately 30 to 40 minutes or until golden brown.
Remove from oven, cut into squares, and garnish with additional blueberries.
Makes 6 to 8 Servings.
Blueberry French Toast Recipe: https://whatscookingamerica.net/fruit/bluefrenchtoast.htm