Heat the sweetened condensed milk, bittersweet and semisweet chocolates and the vanilla in a double boiler over medium-low heat until the chocolate is melted. Stir; the mixture will have a slight marshmallow texture. Remove from the heat, cover and refrigerate until chilled, 2 hours.
Roll the chilled mixture in balls, then roll in the melted milk chocolate to coat. Sprinkle with the chipotle salt.
Chipotle salt is sold in specialty stores.