The origin: Dalgona coffee got its name from the Korean street snack dalgona, which continues to be a nostalgic treat in Korea. It’s made by combining sugar and oil to make a syrup, then adding baking soda. If you are familiar with making hokey pokey or honeycomb from school, you know that once baking soda is added, it quickly foams up in the most magical phenomenon. However instead of letting it harden with all the air bubbles, it is squashed down, making the candy making dense and chewy.
The appeal: Clearly it is the aesthetic nature of the coffee mousse perching pristinely on top of the milk. It’s easy to make with the 1:1:1 ratio (2 tbsp sugar, 2 tbsp instant coffee, 2 tbsp water). You don’t need special kitchen equipment, just a whisk (although hand whisking it takes patience and robust arm strength – neither of which I have).
The science: This is what intrigues me the most. How does the instant coffee turn into such a luscious mousse-like texture? Normally meringue is made by beating egg whites with sugar to stabilise the egg white foam. For dalgona coffee, the coffee is the surfactant providing the firm structure around the bubbles created by whipping the sugar syrup. If you use a hand mixer, the mixing is more uniform, creating more stable smaller bubbles instead of different sized bubbles through hand whisking. The foam becomes thicker not only faster but it’ll last a lot longer on top of the milk.
The taste: The coffee foam itself tastes bitter but once mixed into the milk, it tastes like iced sweet instant coffee. Very sweet. It’s a bit too sweet for me because 2 tbsp of sugar is a lot. You can try experimenting with different ratios, 1.5tbsp works just fine as I’m sure 1tbsp will too.
Why doesn’t it work with matcha? Word is that matcha has a higher fat content than coffee. Anyone who bakes knows that egg whites cannot be whipped into a stable foam if contaminated with egg yolks or any trace of oils in the bowl.
Instead you can try making a matcha whipped cream by whisking 2 tbsp cream with 1 tbsp sugar and adding 1 tsp matcha powder at the end. If it becomes too lumpy, drizzle in more cream to lighten it.