Grate the fresh ginger and strain it to extract about 1 tablespoon of juice into a bowl.
Heat the whole full-fat milk with a small amount of rock sugar until it reaches around 170°F.
Just before pouring, stir the ginger juice to mix it well, as the enzyme tends to settle at the bottom.
Pour the hot milk over the ginger juice without stirring, then cover the bowl and let it sit for 10 minutes.
