Bloom the gelatin. Pour ½ cup of the coffee into a small bowl. Sprinkle the gelatin evenly over the top and leave it for 5 minutes, until the surface looks wrinkled and spongy.

Warm the rest. Heat the remaining 1½ cups coffee with the sugar in a saucepan over medium-low heat until steaming and the sugar has dissolved. Don't let it boil.

Dissolve the gelatin. Take the pan off the heat, add the bloomed gelatin and stir for a minute or two until no grains remain on the spoon.

Pour and cool. Pour into an 8-inch square dish. Let it sit at room temperature for 15 minutes, then skim off any foam for clear, glossy cubes.

Chill. Refrigerate for at least 3 to 4 hours, or overnight, until completely firm.

Cut. Run a thin knife around the edge, then cut the jelly right in the dish into ½-inch cubes. Wipe the blade between cuts for neat edges.

Serve. Spoon the cubes into glasses, pour cold milk or cream over the top, and add ice or a drizzle of condensed milk if you like.