Mystery solved! At the urging of my neighbors, I bought a bag full of this mystery fruit from a fruit cart vendor and loved it. I didn't know what it was called until I saw a package of it at the super market yesterday. I knew the taste was familiar--it is tamarind! I was calling it the "peanut" fruit after the strange shape. I am going to miss all the variety of fruits and vegetables that I can get in Vietnam.
