Add 40g sweetened condensed milk to the bottom of each glass. Set the phin filters directly on top of the glasses if they fit securely, or brew into separate cups and assemble later. The condensed milk should sit as a thick white layer at the bottom. Do not stir it yet. That separation is part of the classical drink structure. Condensed milk's naturally thick, dense consistency is what allows it to settle and hold as a clean base layer without any special handling — this same density is what lets the coffee brewed directly on top of it stay visually distinct rather than immediately blending in.

Divide the ground coffee evenly between the 2 phin filters, 20g per filter. Shake gently to level the bed. Set the press insert on top lightly. Do not clamp it down hard. The coffee bed should be level and lightly compressed, not tightly packed. If you press too hard, the brew chokes and drips far too slowly. A level bed ensures the water passes through the grounds evenly across the whole filter — an unlevel or overly compressed bed creates uneven resistance, forcing water through the loosest spots faster than the rest and producing an inconsistent extraction.

Pour about 15–20ml hot water into each phin just to wet the grounds. Let the coffee bloom for 30–45 seconds. This allows the grounds to expand and start extracting evenly. The grounds should swell slightly and smell intensely coffee-rich. If you skip the bloom, extraction tends to be less even and the brew tastes flatter. Freshly ground coffee releases trapped carbon dioxide when it first meets hot water, and that gas needs somewhere to escape before the main brew begins — the bloom gives it that release, which is what allows the subsequent full pour to extract through evenly saturated grounds rather than around trapped pockets of gas.

Pour the remaining hot water evenly into the phin filters until each has received about 60ml total water. Cover with the phin lids and let the coffee drip slowly into the glasses over the condensed milk. This should take about 4–6 minutes. The coffee should drip steadily, not gush and not nearly stop. Too fast means the coffee bed is too loose and the brew will be weak. Too slow usually means the insert was pressed too tightly. Vietnamese iced coffee needs a concentrated brew. If the coffee is watery, the condensed milk and ice will bury it completely. This slow, steady drip rate is what allows maximum extraction from the dark-roast grounds in the time available — a properly paced brew is genuinely more concentrated than one that drains too quickly, since the water simply hasn't had enough contact time with the grounds in a fast pour.

Once brewing is done, remove the phin filters. At this stage you should see very dark coffee sitting above the condensed milk, with the condensed milk still pooled at the base. Do not stir yet if you want the classic visual. The upper layer should look almost black and dense, while the base stays distinctly pale and thick. That contrast is one of the defining features of the drink before mixing. This is the moment the entire brewing process has been building toward — resisting the urge to stir immediately is what preserves the drink's signature two-tone presentation for as long as possible before serving.

Fill each glass generously with crushed ice. Let the ice sit tightly packed so the drink chills fast and stays properly cold. The ice should be abundant. Vietnamese iced coffee needs enough ice to chill a very strong sweet coffee base without immediately turning watery. Crushed ice's greater surface area relative to its volume chills the drink considerably faster than a few large cubes would — that speed matters here given how strong and concentrated the coffee-and-condensed-milk base is, needing real cooling power to bring it properly cold without excessive dilution time.

Serve with a spoon or straw. Stir just before drinking so the condensed milk fully blends into the coffee. Once stirred, the drink should become a deep caramel-brown colour — strong, sweet, creamy, and bold. It should still taste like powerful coffee first, not just sweet milk over ice. This final stir is what actually combines the drink's two carefully built layers into the finished, unified beverage — everything up to this point has been about building and preserving that separation specifically so this one moment can bring it all together properly.