Place berries in a small bowl and sprinkle with powdered sugar. For the sauce, spoon about 1/4 of the berries, sweetened condensed milk and yogurt into a blender (or food processor) and puree until smooth; set aside.
Cut bread into twelve 1 1/2-inch pieces. Cut into each piece almost all the way through to create a pocket. Stuff the bread slices with remaining sweetened berries and press lightly to close; set aside. Reserve any unused berries to garnish top at serving time.
Whisk egg, egg white, milk, granulated sugar, vanilla and cinnamon in a medium bowl. Heat a large non-stick skillet over medium heat. Spray skillet with non-stick cooking spray. Dip stuffed bread slices in egg mixture to coat and cook until lightly browned on both sides, turning once.
Spoon sauce onto serving plate, arrange French toast on top and garnish with any remaining berries.