I haven't tried it, but it looks like a danged good excuse to open a can of condensed milk! For that matter, it's a good reason to pick up a can of Cafe du Monde coffee, which I'm lucky enough to have stores carrying. (One of the perks of being this close to East Texas.)
Coffee and Condensed Milk
An opened can of sweetened condensed milk is a great excuse to indulge in Vietnamese coffee, called ca-phe sua. To create this jolting beverage, brew an inky-strong cup of coffee. Any full-bodied, dark roast will work, although a perennial favorite of Vietnamese Americans is Cafe Du Monde from New Orleans, which contains chicory. Regardless of the coffee, brew it in a regular electric coffeemaker or a stove-top espresso maker. (The small Vietnamese stainless-steel presses are slow and often don't work well.) If you are starting from beans, grind them extrafine to extract the maximum flavor.
Now, put about 1 tablespoon sweetened condensed milk in a cup. Add about 3/4 cup of your hot, heady brew and stir to combine. Taste and adjust with more milk to your liking, then drink hot as is or pour into an ice-filled glass for a cold version.