3 ounces grapefruit juice, plus 1 slice grapefruit, for garnish
2 ounces gin
4 ounces tonic
Add 1 sprig of mint to a shaker and muddle. Add the grapefruit juice, gin and some ice and shake until well blended. Strain over a glass with ice, add the tonic and mix. Garnish with the remaining mint sprig and a grapefruit slice.