The guanábana—in English, the soursop—is a curious, prickly green fruit often seen in juice form on the streets of Bogotá. While it looks like some kind of videogame dinosaur egg on the outside, its inside is smooth and white. Seth and I must have stumbled upon a mutant species of the fruit because ours weighed a heavy six pounds. We lugged it home, dissected it, and combined the pulp with panela and milk. Our result: a week’s worth of delightfully thick, sweet-and-sour milkshakes.