Make the caramel sauce: In a small, heavy-bottomed saucepan over medium heat, combine the sugar and water. Do not stir. Swirl the pan gently until the sugar dissolves and the mixture turns a deep amber colour — you'll smell a nutty, toasty aroma and see the liquid turn the colour of a new penny. This takes about 5-7 minutes. Immediately remove from the heat and carefully whisk in the double cream. The mixture will bubble up vigorously, so keep your face clear. Add the vanilla and a pinch of salt, stirring until smooth. You should have a glossy, thick sauce that coats the back of a spoon.

Prepare the glasses: Take your serving glasses and tilt them at a 45-degree angle. Drizzle a generous tablespoon of the warm caramel sauce inside the glass, rotating slowly to create swooping, artistic stripes down the sides. Place the glasses in the freezer for 5 minutes to set the caramel against the cold glass.

Assemble the base: Fill each glass with large ice cubes, leaving about 4cm of space at the top. Pour 125ml of the chilled strong coffee over the ice in each glass. You should see the dark coffee settle at the bottom, creating a deep, rich base layer. The sound of the ice cracking slightly as the cold coffee hits it tells you it's working.

Froth the milk: Pour the chilled whole milk into a jar with a tight-fitting lid, filling it no more than halfway. Shake it vigorously for 30-45 seconds until the milk has doubled in volume and looks thick and foamy — you'll hear the sound change from a slosh to a heavier thud. Remove the lid and microwave the jar for 30 seconds to stabilise the foam. The foam should be thick enough to hold a spoon upright.

Layer the drink: Gently pour the frothed milk over the back of a spoon held just above the coffee layer. This technique prevents the milk from mixing violently, preserving the distinct dark-to-light gradient. Pour until the glass is three-quarters full. The texture should be silky and smooth, with a visible separation between the dark coffee and the creamy milk.

Finish with foam and garnish: Spoon the remaining thick foam on top of the milk. Drizzle a final thin ribbon of caramel sauce over the foam in a zigzag pattern. For an extra flourish, add a light dusting of cocoa powder or a tiny pinch of sea salt flakes on top of the foam. The contrast of the white foam, caramel drizzle, and dark dusting is visually stunning.