Instructions

1. 1
   Using a peeler, remove long strips of peel from grapefruit and 2 of lemons. Be careful not to remove any of white pith.
2. 2
   Put the peels into a saucepan. Juice the lemons and grapefruit, and add the juice to the pan.
3. 3
   Using a rolling pin, roll over the rosemary sprigs a few times on a chopping board to release the oils.
4. 4
   Add the rosemary to the pan with ginger, sugar, and water.
5. 5
   Heat for 5 minutes over a low-medium heat, stirring occasionally, to dissolve the sugar.
6. 6
   Reduce the heat to low and cook for 15 minutes until you get a slightly thick syrup. Leave it to cool, then use immediately or chill overnight to develop the flavors.
7. 7
   Strain the cordial syrup through a sieve into a bowl or jug. Transfer to a bottle.
8. 8
   To use, mix 1–2 tablespoons of cordial into ⅔ cup of fizzy water to make a soda, or add to boiling water with 2 tablespoons of whiskey to make a hot toddy.