1/2 cup ice cubes, or as needed, divided
1 lime, zested in thin strips and quartered
1 raw sugar cube
2 fluid ounces fresh Key lime juice
2 fluid ounces vodka (such as Hangar One®)
1 splash club soda (optional)
Fill ice into cocktail glass and place in the freezer.
Place 2 lime wedges and the sugar cube into a cocktail shaker and mash well with a cocktail muddler. Pour in ice, lime juice, and vodka, cover, and shake until the outside of the shaker has frosted.
Remove ice from cocktail glass; wipe dry with a paper towel. Rub a lime wedge around the rim of the glass. Strain the contents into the chilled glass and garnish with a twist of lime zest.