In a tall glass or drink shaker, add the sugar and rosemary. With a muddling stick, crush the sugar with the rosemary until it bruises and becomes more fragrant, a good honest 30 to 45 seconds. Work it! Then pour in the lemon juice and muddle a bit more. Add the vodka and half of the ice, then cover the glass and vigorously shake for about 10 seconds. Pour evenly over the remaining ice in 2 lowball glasses. Drink!