Argentina's Italian immigrants are the reason that Buenos Aires does ice cream so well. The two top makers—once operated by rival branches of the Aversa family—are Persicco and Un' Altra Volta. And porteños still love to debate which one is better. The five Per-sicco outlets (persicco.com) serve such concoctions as marron glacé and sabayon. Un' Altra Volta's two sleek outlets (3060 Avda. Libertador and 2302 Echeverría; 54-11/4783-4048; unaltravolta.com.ar) concentrate on revamped traditional flavors, offering selections like lemon mousse and mascarpone.