Step 1
In a double boiler set over medium-low heat, toss together the dark and milk chocolates, the ancho chile powder, cinnamon, and salt. Add the mascarpone and cream and cook, using a silicone spatula to stir frequently, until mostly melted, about 5 minutes. Turn off the flame and allow the fondue to continue melting over the residual heat, stirring occasionally, until completely smooth, about 5 minutes more.
Step 2
Transfer the chocolate mixture to a fondue pot over a tealight or low sterno flame and serve with toasted brioche, cookies, dates, marshmallows, potato chips, or strawberries, for dipping.