In a large bowl, combine the cocoa powder, rice cereal, oats, coconut, and sesame seeds. Set aside.
In a saucepan over medium heat, stir together the peanut butter, brown sugar, honey, and vanilla. Cook and stir until melted and loose. Pour over the cereal mixture, and stir to coat evenly. Press lightly into a buttered 9×13 inch baking dish. Cool for about 1 hour to firm, then cut into squares.