Prepare the Pistachio Cream Base: In a medium mixing bowl, combine the chilled double cream, pistachio paste, icing sugar, vanilla paste, and the pinch of salt. The mixture will look streaky and slightly grainy at first. Whisk gently by hand or use a small electric frother on low speed. You will see the colour shift from a dark green-grey to a soft, pale pistachio green as the paste incorporates.

Whip to Soft Peaks: Continue whisking. The cream will thicken and start to hold its shape. Stop when you reach soft peaks—when you lift the whisk, the cream forms a gentle, drooping peak that doesn't immediately fall flat. The texture should be silky and smooth, not stiff or buttery. You'll hear the sound change from a slosh to a quieter, thicker swish.

Assemble the Glass: Fill a tall glass to the brim with ice cubes. Pour the whole milk over the ice, filling the glass about one-third full. The milk will immediately chill and create a cloudy layer at the bottom.

Add the Coffee: Gently pour the chilled coffee or cold brew over the milk and ice. Pour slowly down the side of the glass to preserve the distinct layers. You will see a dark, rich brown layer sitting above the milk, with the ice bobbing at the top.

Top with Pistachio Foam: Using a large spoon, carefully dollop the whipped pistachio cream over the coffee. Spread it gently to the edges of the glass. The foam should sit thickly on top, creating a distinct pale green cap. It will feel heavy and luxurious on the spoon.

Garnish and Serve: If using, sprinkle a few crushed pistachios over the foam. Serve immediately with a straw or a spoon. The first sip will pull the creamy foam through the bitter coffee, creating a perfect balance of flavours and temperatures.