How to Make It
Place grapefruit peel strips in a medium bowl. Add gin, and let stand for 24 hours. Strain; discard solids.
Place plums and simple syrup in a blender, and process on high until smooth, about 1 minute. Transfer to an airtight container, and refrigerate until ready to use.
Salt the rim of a double old-fashioned glass with salt. Fill glass with ice. Combine grapefruit juice, lime juice, 11/2 ounce Grapefruit-Infused Gin, and 3/4 ounce Boshi Syrup in a cocktail shaker filled with ice. Cover and shake until chilled, and strain into prepared glass. Garnish with a red ball pick fitted with grapefruit triangles and pâte de fruit.