Make the simple syrup:

• Bring water, rosemary and sugar to a boil in a small saucepan. Stir with a wooden spoon until the sugar disolves. Let cool. Pour into a glass jar and chill at least 30 minutes. Remove the rosemary. Keeps in the fridge up to 3 weeks.
• In a clean dish towel, wrap up about 8-10 cups of ice. Pound the ice with a rolling pin until crushed. Place half the ice into a cocktail shaker and then other half into two double old fashioned glasses.
• In a cocktail shaker, add the Grand Mariner, Papplemouse, gin, simple syrup and juices. Shake well until the cocktail shaker is frosted over- about 15 seconds.
• Using the strainer, pour into glasses, Top with sparkling water. Stir well. Garnish with grapefruit peel and a sprig of washed rosemary.