Muddle Basil leaves in a cocktail shaker
Fill shaker with ice
Add Tequila, Mezcal, Watermelon Juice, Lime juice, Agave Syrup (saline if desired) and shake till well chilled
Rim rocks or margarita glass with Chamoy and Tajín
Strain cocktail into the glass filled with ice
Garnish with Chamoy candy or lime slice