I you mean Theobroma cacao, the plant that chocolate is made from, sure you can, but it's probably not going to be much of a bonsai. The plant has very large leaves (6 inches by 3 inches) on gangly stems with long internodes.

Those traits will be extreemly hard to overcome, as this is an understory tree in the tropics.It developed those characteristics to handle that envronment.

Here is a link that might be useful: Theobroma cacao