A shrub syrup, which appears in this cocktail, is a delicious, vintage-style syrup made with fruit, sugar, and a form of acid (in this case, vinegar). This cocktail was served at a Hendrick's Gin Voyage into the Unusual.
Combine gin, liqueur poire, lemon juice, ginger syrup, and apple shrub in a cocktail shaker filled partway with ice. Shake well and strain into an iced long glass. Top with cider and garnish with an Angostura bitters-soaked and toasted slice of pear.