Remove lid and metal screen from phin filter. Add ground coffee to brewing chamber and shake gently to distribute evenly. Gently push the screen back on until you meet some resistance. (Don’t push the screen all the way down, as it will take longer for coffee to drip and result in an extra strong brew.)

Place lid underneath filter and set on a plate large enough to hold the filter and lid so it can catch any spilled coffee. Add ¼ cup (60ml) hot water water and let steep until coffee grounds have absorbed all the water and turn black, about 5 minutes. While coffee steeps, place condensed milk into a glass big enough to hold 8 to 12 ounces.

Place filter over glass containing condensed milk. Pour in remaining ¼ cup (60ml) hot water and any coffee that seeped out during steeping process. Allow coffee to drip until all liquid has drained, 7 to 10 minutes. (If it stops dripping because the screen was screwed on too tightly, gently loosen the screen.) Remove filter. Stir coffee and sweetened condensed milk to combine. Add ice, stir, and serve immediately.