Slice the bread into 3/4 inch think slices and arrange in a single layer in a 9†x 13†dish. (I don’t use the full loaf—only about 8 slices—whatever will fit.) Whisk the eggs, milk, baking soda and vanilla in a medium bowl until smooth. Pour gradually over the bread, turning the bread to coat it completely with the egg mixture. Cover with plastic wrap and put in the refrigerator overnight. Combine the blueberries, sugar, cornstarch and cinnamon in a bowl and mix well. (I usually do this when I prepare the bread the night before and keep it in the refrigerator overnight). In the morning, spread the blueberry mixture over the bottom of a buttered 9†x 13†baking dish. Place the bread, wettest side down, over the blueberries. Brush with the melted butter. Bake in a 450 degree oven for 20 to 25 minutes or until golden brown on top. Garnish with powdered sugar.