Add the peaches, lavender, sugar, and vinegar to a medium pot and heat on medium heat. Bring the mixture to a boil and mash the peaches while you stir it. Once the mixture has come to a boil, turn off the heat and let it cool completely. Strain and store in an airtight container. A mason jar works great!
MAKE THE COCKTAIL
Add all the ingredients to a martini shaker and shake well. Pour into glasses and garnish with a sprig of lavender.
ANOTHER WAY TO MAKE A SHRUB
Add the peaches, lavender and sugar to a large mason jar or a bowl. Mash the peaches up a bit. Then let the mixture sit in the fridge for at least a few hours or up to a couple days. Strain the juice and add the vinegar to the juice. Shake or stir well and thats it.
If you have elderflower syrup instead of elderflower liqueur, you can just use 4 oz of gin and 1 oz of elderflower syrup