Mix coconut milk and ube extract to make ube milk.
Fill a 12 oz glass (or larger) with ice. Pour in ube milk and sweetener, if using.
To create a layered look, gently pour your 1/4 cup strong coffee or espresso, aiming the stream to hit the ice instead of the milk. Stir and enjoy.
Notes
I actually prefer a slightly weaker ube flavor, using 1/8 tsp of extract for about 1 1/2 cups of milk, which is enough to split between two 12 oz glasses. It's completely a matter of taste how much extract you want to use.
1/4 cup is about the volume of two espresso shots, but you can also use Moka coffee, Vietnamese coffee, or even a strongly made instant coffee. For a weaker coffee flavor you can use drip or cold brew as well.