To prepare the ginger-infused vodka, combine the vodka and ginger root in a clean container. (Reserve the vodka bottle for storing the infused vodka later.)
Seal the container and store in a cool, dark place for 3 days, shaking or stirring occasionally. After 3 days, pour the vodka through a strainer and discard the ginger solids.
Return the strained, ginger-infused vodka to its original bottle. Store infused vodka in the refrigerator for up to 1 month.
To prepare the cocktail, pour all the ingredients into a martini shaker. Shake vigorously for 30 seconds. Strain into a chilled martini glass, rimmed with sugar.
Garnish with 2 slices of fresh, ripe pear or 1 ginger slice.