Cold brew coffee is super easy:
If you have a French press (cafetière) you already have everything you need.
Simply buy your favourite coarse ground beans, or grind you beans yourself on the coarsest possible setting.
Make the coffee by pouring 3 parts room temperature water over 1 part coffee grounds, and leave to steep for 24-48 hours, with the press pushed down just a milimetre under the surface of the water, so that no grounds float above.
When you are ready, push the plunger as you would hot coffee.
Now you have a highly concentrated cold brew coffee.
You can dilute it 1:1, or ot suit your taste.
To make it 'Vietnamese'
Place ice cubes in a DOPPLER glass, and pour over sweetend condensed milk.
Then simply pour over your diluted cold brew.
Cold brew lasts for about a week in the fridge (much longer than hot coffee that has cooled)