Combine the Splenda, cocoa powder and 2 tablespoons of the boiling water in a small heatproof bowl and blend until smooth.
In another small heatproof bowl, combine the remaining boiling water with the gelatine and leave for 1 minute until it becomes spongy.
Stir briskly with a fork until the gelatine dissolves, then set aside to cool for 5 minutes. Stir in the cocoa mixture.
Place the evaporated milk in a large bowl and beat with electric beaters for 1–2 minutes or until light and fluffy.
Fold in the cocoa mixture with a metal spoon, mixing it until smooth. Transfer the mixture to a jug and stir to combine.
Immediately pour the mixture through a fine-meshed sieve into four ½ cup (125 ml) capacity serving pots or glasses.
Cover with plastic film and chill in the fridge for 4–5 hours until set.
Dust with extra cocoa powder and serve.