Add the sugar, water, dried lavender buds, and salt to a small saucepan. Warm over medium heat, stirring until the sugar fully dissolves. Bring just to a gentle simmer, then remove from the heat. Let the lavender steep for 5 minutes. Stir in the vanilla if using. Strain the syrup through a fine sieve and let it cool completely. The syrup should smell floral and clean, not aggressively perfumed. Lavender becomes soapy very quickly if over-steeped, so keeping the steep short is one of the main control points in the recipe. This precisely timed steep is worth treating as a genuine technical requirement rather than a rough guideline — lavender's aromatic oils extract disproportionately fast relative to many other dried botanicals, and even a few extra minutes of contact time can tip the syrup from pleasantly floral into something closer to soap.

Brew 120ml espresso total, equal to 4 standard 30ml shots. Let it stand for 30–60 seconds only if it is extremely hot, but do not let it sit long enough to lose freshness. The espresso should be fresh, balanced, and aromatic. Lavender is delicate, so harsh or burnt espresso will dominate the drink and flatten the floral character. A genuinely clean, well-balanced shot is what lets the lavender's subtle floral note register clearly alongside the coffee — anything sharp or bitter in the espresso simply overwhelms that delicate flavour rather than sitting alongside it.

Add 15ml lavender syrup to each glass. Add a small splash of the cold milk to each glass and stir briefly to loosen the syrup. This step matters because syrup left sitting in a heavy layer at the base gives uneven sweetness and uneven lavender flavour. The drink should start with the syrup already partially dissolved. Loosening the syrup while the glass is still simple and mostly empty gives it a genuine, direct chance to disperse evenly, rather than attempting the same mixing later once ice and the remaining milk are already in place.

Fill each glass generously with ice. Pour 150ml cold milk into each glass over the ice. The glasses should look very pale and milk-forward. The lavender effect in the drink should stay soft and subtle. If the base already looks dark or overly tinted, the balance is wrong before the espresso even goes in. Checking the colour at this intermediate stage, before the espresso is even added, gives a useful early warning if the syrup-to-milk ratio has already drifted too concentrated.

Pour 60ml espresso into each glass over the milk and ice. Let it swirl naturally for a moment, then stir briefly. The finished liquid should settle into a very pale beige-lilac or soft grey-mauve impression rather than a strong purple drink. The colour should be barely there but visible, and the drink should still clearly read as a latte. This specific, deliberately understated colour target functions as a genuine diagnostic for the drink's balance — a result that reads as a strong, visibly purple drink signals either too much syrup or too much colouring relative to the milk and espresso.

If you want the more polished café-style finish, froth the extra cold milk very lightly until it forms only a thin soft foam. Spoon a small amount over the top of each drink. The foam should stay minimal. Too much foam turns the drink into something closer to an iced cappuccino. The correct finish is only a light surface layer. Stopping well short of a substantial foam is what keeps this drink's presentation reading as delicate rather than pushing toward a heavier, more filling format.

Rest 1 small dried lavender sprig across the rim of each glass and serve immediately. The garnish should stay restrained and aromatic. It should suggest lavender, not make the drink look overloaded or potpourri-like. This same restraint applies to the garnish as it does to the syrup itself — a single small sprig completes the drink's elegant presentation without tipping it toward looking fussy or decorative for its own sake.