Place bread into a jelly roll pan. In a medium bowl, mix eggs, half-and-half and vanilla together, pour over bread, cover and refrigerate overnight. Combine agave, cardamon, and cornstarch together, gently mix in peaches and raspberries and place in a greased 13″x9″ baking pan. Place chilled bread mixture on top of blueberry mixture; drizzle butter over bread. Bake at 400 degrees for 30 minutes or until golden brown.