Rinse six 120 ml ramekins or molds with cold water and set them upside down to drain. This helps the set pudding release cleanly later.

In a 3-quart / 2.8 L saucepan, whisk the cornstarch, sugar, and salt together. Slowly whisk in about 150 ml of the milk until you have a smooth paste with no lumps.

Whisk in the rest of the milk, then set the saucepan over medium heat.

Cook, whisking constantly and scraping the corners of the pan, for 8 to 10 minutes, until the mixture thickens and coats the back of a spoon in a thick ribbon. It should bubble gently at the edges. If you stop whisking, it will catch and form lumps on the bottom, so keep moving.

Take the pan off the heat and stir in 1 tablespoon of rosewater.

Divide the pudding between the molds, tapping each one on the counter to release air bubbles. Let them cool at room temperature for 20 minutes.

Cover the molds and chill for at least 4 hours, until the pudding is fully set and holds its shape when you tilt the mold.

While the pudding chills, combine the water and sugar for the syrup in a 1-quart / 1 L saucepan. Simmer over medium heat for 3 to 4 minutes, until the sugar dissolves and the syrup looks slightly thickened.

Remove from the heat and stir in the remaining 1 tablespoon of rosewater. Let the syrup cool completely before using.

Run a thin knife around the edge of each mold, then invert onto a small plate to unmold, or serve straight from the ramekin.

Drizzle each pudding with rosewater syrup and sprinkle with shredded coconut and crushed pistachios. Serve cold.