Heat the sweetened condensed milk in a small saucepan just until the edges start to bubble, stirring constantly. Do NOT allow to boil.
Place the chocolate in a medium-sized heat-proof bowl. Pour the hot milk over the chocolate and allow to sit for two minutes. Add in the vanilla, sea salt, cinnamon, and cayenne powder and stir until the chocolate is fully melted.
Cover and refrigerate until chilled, around 1 hour. Mixture should be firm but not hard.
Roll the chilled mixture into small balls then roll into your choice of garnish.
Serve truffles at room temperature. Store leftovers in the refrigerator.