Drain the lychees and reserve the syrup. Measure 350 ml of syrup into a saucepan, topping up with water if needed to reach 350 ml total. Add 150 ml of water.

Whisk in 1 tsp of agar-agar powder and 1 tbsp of caster sugar while the liquid is cold. Stir until dissolved.

Bring the mixture to a gentle boil over medium heat, stirring constantly. Simmer for 2 minutes until the agar-agar is fully activated and the liquid is clear. Skim any foam from the surface.

Halve the lychees and arrange them in the bottom of a lightly rinsed 8x8 inch dish or divide among individual cups.

Pour the hot lychee syrup mixture over the lychees through a fine-mesh sieve. Let the layer cool at room temperature for 20 to 25 minutes until it holds a finger impression but is not fully firm.

Combine the coconut milk, 100 ml water, 1 tsp agar-agar powder, and 3 tbsp caster sugar in a clean saucepan while cold. Whisk well to combine.

Heat over medium heat, stirring constantly, until the mixture reaches a gentle boil. Simmer for 2 minutes until the agar-agar is fully dissolved and the coconut milk is smooth. Add pandan extract if using and stir through.

Remove from heat and let it cool for 3 to 4 minutes, stirring occasionally, until it is warm but not scorching.

Check the lychee layer is partially set. Place a spoon just above the surface and pour the coconut mixture slowly over the back of the spoon to disperse the liquid gently. This prevents the two layers from mixing.

Let the assembled jelly sit at room temperature for 10 minutes, then transfer to the fridge uncovered for at least 2 hours, or until completely firm throughout.

Once fully set, run a thin knife around the edges of the dish. Slice into rectangles or cubes and lift out with a flat spatula. Serve cold.