Tear or fold each kaffir lime leaf in half to crack the midrib and expose the oils. This takes 20 seconds and makes a noticeable difference in how much aroma the syrup develops.

Combine the sugar and water in a small saucepan over medium heat. Stir for 2 to 3 minutes until the sugar is fully dissolved and the liquid is clear.

Remove the pan from the heat and add the bruised kaffir lime leaves. Stir once to submerge them.

Steep for 10 to 12 minutes - set a timer. At 10 minutes you get a clean floral note. Past 12 minutes bitterness starts to build and can't be reversed.

Pour the syrup through a fine-mesh sieve into a clean jar or heatproof jug. Discard the leaves. Allow to cool to room temperature, then refrigerate until fully chilled before using, about 20 minutes in the freezer or 45 minutes in the fridge.

Fill two tall glasses with ice cubes.

Add 2 tablespoons of the chilled kaffir lime syrup to each glass and stir briefly to coat the ice.

Pour 120 ml of cold brew concentrate into each glass over the syrup and ice.

Pour 60 ml of coconut milk slowly along the inside edge of each glass. It will drift down through the coffee, creating a layered effect. Stir before drinking or leave layered for serving.

Float one fresh kaffir lime leaf on top of each glass if serving to guests. Serve immediately.