Coffee was introduced into Vietnam by French colonists in the late 19th century. Vietnam quickly became a strong exporter of coffee with many plantations in the central highlands. The beverage was adopted with regional variations. Because of limitations on the availability of fresh milk, the French and Vietnamese began to use sweetened condensed milk with a dark roast coffee.
Vietnamese iced coffee, also known as Ca phe da or cafe da (Vietnamese: cà phê đá, literally "coffee ice") is a traditional Vietnamese coffee recipe.
"Vietnamese iced coffee with milk", also known as ca phe sua da or cà phê sữa đá It is also called ca phe nau da (Vietnamese: cà phê nâu đá, "iced brown coffee") in northern Vietnam.
At its simplest, Ca phe da is made with finely ground Vietnamese-grown dark roast coffee individually brewed with a small metal French drip filter (cà phê phin) into a cup containing about a quarter to a half as much sweetened condensed milk, stirred and poured over ice.
In the USA, Vietnamese-style coffee is sometimes confused with that brewed in Louisiana with French roast coffee with chicory. Vietnamese immigrants who came to the state in the late 20th century adopted New Orleans-style coffee because they were unable to get Vietnamese-grown coffee. The French roast style popular in Louisiana was similar to Vietnamese coffee in its relatively coarse grind; therefore it made an excellent substitute for traditional brewing in the single-serving filter/brewer. In Vietnam, however, locally produced coffees are characterized by medium roast and seldom contain chicory.
source : Vietnamese Coffee