Add one shot of tequila and one shot of dark rum (add more to taste). To get nice layers between your alcohols, add the tequila first and then the rum.
Cut your lime in half and squeeze the juice into the glass.
Top it off with some ginger beer, leaving some room at the top of the glass.
Pull an espresso shot, then slowly add the espresso shot to your cocktail glass (you do not have to use the entire shot).