Deseed watermelon and cut into chunks.

Puree watermelon using a hand blender until smooth.

Strain the puree into a bowl and measure 2 cups, reserving 5 teaspoons.

In a small bowl, stir cornflour with 1/4 cup watermelon puree until smooth.

In a saucepan, combine watermelon puree, cornstarch mixture, sugar, vanilla extract, and cinnamon stick.

Bring the mixture to a boil over medium heat, then simmer for 10-15 minutes, stirring continuously until thickened.

Rinse ramekins with water; do not dry.

Pour the watermelon pudding mixture into the ramekins.

Cover with plastic wrap and refrigerate for 6 hours.

To serve, remove the plastic cover.

Serve in ramekins or unmold the pudding.

To unmold, rub ramekin between palms and invert onto a plate, giving it a firm tap.

Garnish with ground cinnamon powder and chopped walnuts.