Heat oven to 325 degrees. Line an 8-inch square pan with nonstick aluminum foil making extended edges, or can use regular foil and coat with cooking spray; set aside.
In large bowl of electric mixer, combine oats, Grape Nuts, flours, flaxseed, cinnamon, and salt; stir to combine. Add egg, banana, honey, brown sugar, oil, and vanilla; mix well. Stir in chopped prunes, walnuts, chocolate chips, and sesame seeds. Mix well to combine; dough will be stiff. Transfer to prepared baking pan and pat in mixture evenly. Bake for 30-35 minutes until edges are browned. Cool completely on wire rack in pan. Use edges of foil to pick up and flip out onto a cutting board and cut into 24 squares.