Place bread cubes into a greased 9 x 13 pan (this makes a full pan). Spread blueberries over the bread. Beat cream cheese, 1/2 sugar, 1 tsp. vanilla and sour cream until smooth. Carefully spoon over blueberries. Cut 8 or 10 1-inch slices of French bread, place over the berries.
Beat the eggs well, add the remaining 1/2 cup sugar, 1 tsp. vanilla, milk, half-and-half; beat again. Pour the egg and milk mixture over the French bread slices. Cover and refrigerate overnight.
Remove from refrigerator about 45-60 minutes before baking. Stir together topping ingredients; spread carefully over the bread.
Bake uncovered at 350°F for 60-90 minutes, or until bubbly. You may need to cover with foil the last 15 minutes to keep it from getting too brown. Let stand for about 10 minutes before cutting. Spring with powdered sugar if desired.