It's brewed drop by drop through a small metal phin filter balanced right on top of the glass — a single cup can take five minutes just to drip through.
Robusta coffee grounds sit in a phin filter over a glass with sweetened condensed milk, dripping slowly until the coffee and milk mix; it's then stirred and poured over ice. Vendors on low plastic stools sell it on nearly every sidewalk corner, often alongside bánh mì carts.