How to Make It
Add about a cup of the water to the powdered gelatin in a small bowl and allow it to stand for about 10 minutes. Bring the remaining water—about three cups—to a low simmer then add the coffee and sugar, whisking to dissolve the sugar.
Add the gelatin mix to the coffee liquid and whisk well to ensure all the gelatin crystals are dissolved. (You may need to rinse the gelatin bowl with the hot coffee liquid a few times to remove any crystals still clinging to the bowl.)
Pour the coffee liquid into a shallow cake tin to a depth of about 2 centimeters. Refrigerate for 4 hours, or until the jelly is well set.
To serve, cut the jelly into 2 centimeter cubes and serve with a few spoonfuls of thickened cream.