Set your filled phin filter on top of the glass containing condensed milk. Slowly pour just about two tablespoons of hot water initially, allowing the coffee grounds to expand (bloom) for about 30 seconds. Then fill the phin with hot water and place the lid back on. Allow your coffee to slowly drip directly onto your condensed milk. Usually, this brewing process lasts around 4 to 5 minutes.
For more detailed tips on this brewing method, see our full guide:
How to Make Vietnamese Coffee.