Method

• 1.
  Place sugar and 1 tbs boiling water in a heatproof jug and stir until sugar dissolves. Chill until completely cold.

• 2.
  Place salt flakes on a small plate. Rub the rims of 4 margarita glasses with the lime wedges, then twist through salt flakes to coat. Set aside.
• 3.
  Add blueberries, lime juice and ginger to a cocktail shaker, then muddle together with a muddling stick or the end of a rolling pin, breaking up berries. Add tequila, chilled sugar mixture, a few drops of bitters and a handful of ice.
• 4.
  Shake vigorously for 20 seconds, then strain into the prepared glasses and serve immediately.