This is a recipe for homemade grapefruit shrub that was first used in the Rosemary Gin & Tonic, a winter-inspired variation of the classic Gin & Tonic.
Juice grapefruit, measure out 180 ml grapefruit juice, and keep grapefruit peels.
Add 300 g sugar, 180 ml apple cider vinegar, 180 ml grapefruit juice, 120 ml hot water, 1 tsp pink peppercorns, and grapefruit peels to a saucepan.
Muddle grapefruit peels and pink peppercorns for 5-10 seconds.
Heat over medium heat while stirring for 5 minutes.
Cover pan, reduce heat to low, then let simmer while stirring occasionally for 10-15 more minutes.
Remove from heat and let cool for 5 minutes.
Strain shrub through a fine mesh strainer 1-2 times to remove grapefruit peels, pink peppercorns, and any sugar particles.
Pour shrub into a squeeze bottle or pouch with a spout using a funnel, then refrigerate or freeze.