Chop the chocolate very finely, this helps it to melt easily, place it in a heat proof bowl. Add the butter to the bowl. Reserve.
Heat the cream in a small saucepan over medium heat with the mulato chilli. Gently bring to the simmer, add the tonka bean / vanilla essence and the agave worm salt. Pour the warm cream over the reserved chocolate and leave it to sit for a minute. Stir gently from the centre outwards, making sure all the chocolate gets melted. Add the mezcal, stir to incorporate, then cover and refrigerate for 2-4 hours or until set.
When the truffle mix has set, scoop little balls with a teaspoon or melon baller, about 15g in weight. Roll them between your palms until perfectly spherical and place them on parchment. Roll in your chosen coating and place on a tray. These will keep for 5 days in the fridge or can be frozen, serve at 15oC.