Make the Brown Sugar Syrup: In a small saucepan, combine the brown sugar and water. Place over medium heat and stir gently until the sugar dissolves completely—you'll see the liquid turn from grainy to glossy and clear, and you'll smell a warm, caramel-like sweetness. Once it bubbles gently, remove it from the heat and stir in the vanilla and salt. Let it cool for 5 minutes; it will thicken slightly as it cools.

Brew Your Coffee: While the syrup cools, brew your coffee or espresso. Aim for a strong concentrate—about 200ml—so it doesn't get lost behind the milk and ice. The coffee should be hot, dark, and aromatic, with a rich crema if you're using an espresso machine.

Prep Your Glass: Fill a tall glass to the brim with ice cubes. The sound of the ice clinking against the glass is your cue that you're ready to build the drink. For a prettier presentation, you can rim the glass with a little extra brown sugar.

Assemble the Syrup: Pour 2 tablespoons of the cooled brown sugar syrup over the ice. You'll see it pool at the bottom, creating a dark, sweet base. If you prefer a sweeter drink, add another half tablespoon—it's entirely up to you.

Add the Coffee: Pour the hot coffee over the syrup and ice. The ice will crackle and pop as the hot liquid hits it—that's exactly what you want. Stir briefly with a long spoon to combine the syrup and coffee; the colour should become a uniform deep brown.

Top with Oat Milk: Slowly pour the oat milk over the back of a spoon held just above the coffee layer. This technique creates a beautiful layered effect—the milk will sit on top of the coffee, creating a pale, creamy crown. Watch for the line where the two liquids meet; it should be distinct at first.

Finish and Serve: Give the drink one final gentle stir (or leave the layers intact for a visually stunning serve). Add a cinnamon stick or a dusting of ground cinnamon on top. Serve immediately with a straw or a long spoon.