Whenever Star Apple is in season, most abundant during summer, my mother would make a "pampalamig". This is the kind I never heard of being done by anyone else till now except us her siblings. She'd scrape off the pulp together with the seeds in a big bowl, put condensed milk and ice. That's just it!
Inspired by this, I tried it in a shake. I commend to choose the very sweet kind or the taste won't come out. Don't depend on milk or sugar or it'll turn out just a plain milk shake, instead. I use three large pieces to make a liter.