Freeze the peeled and pitted avocados for 1 hour – they need to be partly frozen but still pliable. Juice three of the limes, reserving the fourth for garnish. Using a cocktail shaker or a blender, combine the lime juice, frozen avocado, coriander (stalks included) and tequila and shake or blitz until smooth. Pour in the lemonade and shake or blitz once more. 

Rub the rims of four highball glasses with lime juice and dip into a saucer of sea salt. Fill each glass with the margarita mixture and garnish with a slice of lime. Serve immediately.