Soak the cassava tubers in a tub, pond, or stream for three days or longer.
Peel the tubers, and wash them in large tub, changing water several times.
Use a mortar and pestle to pound the tubers into a thick, smooth paste.
Put the paste into the leaves, fold them into packets, and tie them closed (make the packets uniform in size. Two sizes are common in central Africa: either 1 to 2 inches in diameter by 12 inches in length; or 4 inches in diameter by 12 inches in length).
Place sticks or a wire basket in the bottom of a large pot.
Stack the packets on the sticks, add enough water to steam-cook them (the water level should be below the packets).
Cover tightly and boil for four to eight hours.
The finished baton de manioc should be very thick and solid—thicker than mashed potatoes, nearly the consistency of modeling clay.
Baton de manioc is served warm or at room-temperature, with soup, stew, or any sauce dish.
The cooked baton de manioc will keep for several days, if kept in the leaf-wrapper in a cool, dry place.