Using a sharp, serrated knife, cut a horizontal pocket in each bread slice, coming close to the edges but leaving crusts intact. Be careful not to cut holes in the dough. In a small bowl, mash the banana with a fork. Fold in the strawberries and peanut butter. Using a spoon, stuff each piece of bread with the banana/strawberry mixture but do not allow stuffing to overflow pocket. In a shallow bowl, lightly beat the egg and egg whites and combine with milk, salt, sugar, and cinnamon. Dip the stuffed bread slices in the egg mixture and let soak about 10 minutes, turning occasionally, until liquid is absorbed.Melt the butter in a large cast iron or nonstick skillet over medium heat. Toast the bread in the hot pan until cooked through, about 3 minutes per side. Serve topped with warm honey, pure maple syrup or jam.