01 - Strain the fresh watermelon juice through a fine mesh sieve to eliminate all pulp and seeds, ensuring a smooth liquid base.
02 - In a medium saucepan, whisk together the granulated sugar and cornstarch until thoroughly blended and no lumps remain.
03 - Gradually pour the strained watermelon juice into the saucepan while whisking continuously to create a smooth, lump-free mixture.
04 - Stir in the fresh lemon zest and vanilla extract (or vanilla powder) until evenly distributed throughout the mixture.
05 - Place the saucepan over medium heat, stirring constantly to prevent scorching. Cook for 8 to 10 minutes until the mixture thickens to a soft pudding consistency that coats the back of a spoon.
06 - Remove from heat and gently fold in the mini dark chocolate chips if desired, distributing them evenly to simulate traditional watermelon seeds.
07 - Pour the pudding into individual serving glasses or molds. Allow to cool to room temperature, then refrigerate for at least 3 hours until completely set and firm.
08 - Just before serving, generously sprinkle the surface with finely chopped pistachios. Add dried rose petals and extra dark chocolate chips as desired for an elegant presentation.