Combine the agave and avocado in a bowl and mash until smooth. Add the ascorbic acid and stir to combine (this will keep the avocado from turning brown). Press the avocado mixture through a fine-mesh strainer for a smooth puree.
Add the rum, lime juice and 2 heaping spoonfuls of the avocado puree to a small cocktail shaker. Add some ice and shake long and hard. Pour through a fine-mesh strainer into a coupe glass. Garnish with a small pinch of salt.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.