Whisk the 16g high-methoxyl confectioner's pectin thoroughly into the 175g caster sugar in a dry bowl — dispersing the pectin through the sugar before adding liquid prevents lumping.

Pour the 250ml cold water into a small saucepan. While whisking constantly, rain in the sugar-pectin mixture in a slow, steady stream.

Place the saucepan over medium heat, whisking frequently, and bring the mixture to a full boil (100°C). Hold at a gentle boil for 2 minutes to fully hydrate and activate the pectin.

Remove from heat, pass through a fine-mesh sieve into a clean container, and cool to room temperature. The base will be a thin, glossy syrup. It can be refrigerated for up to 3 days.

Combine the 150ml freshly strained lime juice with the 17g caster sugar and stir to dissolve.

Vacuum-seal the mixture in a plastic bag (or place in a zip-lock bag, pressing out all air, sealed tightly). Alternatively, pour into a small jar with a tight lid.

Set your water bath to exactly 70°C. Submerge the sealed bag or jar and hold at 70°C for 10 minutes.

Remove and immediately cool in an ice bath until the juice reaches below 5°C. Refrigerate until needed; use within 24 hours for best flavour.

In a bowl, whisk together 120ml of the cooled pectin base, 120ml of the pasteurised lime juice, 5g matcha powder, 1.5g malic acid, and 20ml vodka until the matcha is fully dispersed with no lumps — the mixture will be intensely green.

Add the 60ml egg whites and whisk briefly to combine evenly. Do not over-whip at this stage; the cream whipper will aerate the mixture.

Pass the mixture through a fine-mesh sieve to remove any undissolved matcha particles.

Pour the sieved liquid into the 500ml iSi cream whipper. Seal, charge with 2 N2O cartridges (charging one at a time, shaking well between each charge), and refrigerate the whipper for at least 30 minutes, preferably 1 hour, to chill thoroughly.

SAFETY FIRST: Work in a well-ventilated area. Wear cryogenic or heavy silicone gloves and eye protection. Never put liquid nitrogen in a sealed container. Keep the LN vessel stable on a flat surface away from bare skin.

Pour 1–2 litres of liquid nitrogen into a wide, deep insulated bowl or the dewar. Allow the vigorous boiling to subside slightly.

Hold the charged iSi whipper horizontally, shake once, and dispense a rounded mound of mousse (approximately 25–30ml, roughly the size of a golf ball) onto a metal dessert spoon. Use a second spoon to shape it into a neat quenelle if desired — work quickly as the mousse is fragile.

Lower the spoon gently into the liquid nitrogen, submerging the mousse. Hold for approximately 8–10 seconds to freeze the outer shell, then carefully flip the quenelle using a second spoon and freeze the other side for a further 8–10 seconds.

Lift the frozen mousse out of the nitrogen with the spoon and allow any excess nitrogen to evaporate for 3–5 seconds. Test: the mousse should hold its shape cleanly and be firm enough to transfer to a plate, but the interior should not be fully frozen solid.

Transfer each quenelle carefully to a small chilled serving plate or spoon. Immediately dust lightly with matcha powder through a fine tea sieve.

Serve at once — within 15–20 seconds of leaving the nitrogen. The mousse should dissolve completely and coldly on the tongue, delivering a burst of sweet, sour, grassy green tea flavour. Repeat for remaining portions, working in batches.