Put the ice in a cocktail shaker and add the lemon juice, grenadine, sugar syrup, gin and cherry brandy.
Shake vigorously until a frost forms on the cocktail shaker.
Strain into two highball or rocks glasses filled with crushed ice. Top up with soda water if desired and stir.
Garnish with lemon strip or fresh cherries, add a paper straws and serve.
Notes
HOW TO MAKE CRUSHED ICE: Put plenty of ice cubes in the middle of a clean lint-free tea towel. Close up the towel around the ice and use a rolling pin to crush it into small pieces. Use immediately.HOW TO MAKE CHERRY BRANDY: A pretty easy way to make cherry liquor using cherries and brandy or vodka. Fill a clean large jar (1 quart jar) with 225g (1 cup) pitted cherries. I usually use frozen pitted cherries, defrosting them first.
Add 200g (1 cup) sugar and half a cinnamon stick. Gently muddle the cherries with end of a clean rolling pin then top with 1 bottle of vodka (750ml) or a mix of vodka and brandy if you prefer. Seal the jar and shake. Put in a cool dark place for a week, turning over daily.
Strain the liquid through a fine sieve into a clean bottle and store in the fridge to use in cocktails. Discard the cherries.