Lightly brush 4 individual ramekins or dariole molds (150-180 ml each) with neutral oil. Set aside on a small tray.

Pour the coconut milk into a medium saucepan. Add the agar-agar powder and whisk immediately until no dry powder is visible. Do this before heating to prevent lumps.

Place the saucepan over medium heat. Add the sugar and salt. Stir steadily as the mixture warms up.

Bring the mixture to a full rolling boil, then reduce to a steady simmer. Cook for 2 minutes, stirring constantly, until the agar-agar is fully activated and the mixture looks smooth and slightly glossy.

Remove from heat. Stir in the vanilla extract.

Pour the mixture through a fine-mesh sieve into a heatproof jug. This removes any undissolved agar and gives a cleaner texture.

Divide the mixture evenly between the prepared molds. Leave to cool at room temperature for 20 minutes, then transfer to the refrigerator.

Chill for at least 4 hours, or overnight, until fully set and cold throughout.

To unmold, run a thin knife around the inside edge of each mold. Place a serving plate on top, then invert with one firm motion. The panna cotta should release cleanly.

Spoon passion fruit pulp, mango coulis, or toasted coconut flakes over each panna cotta and serve immediately.