Combine sugar, marshmallow cream, evaporated milk, butter, coffee-flavored liqueur, and salt in a heavy saucepan over medium heat. Bring to a boil, stirring constantly. Remove from heat; stir in semisweet chocolate chips and milk chocolate chips until melted. Add pecans and vanilla extract.
Line an 8-inch square baking dish with aluminum foil, leaving an overhang on 2 opposite sides. Pour in chocolate mixture. Refrigerate fudge until firm, about 2 hours. Lift out of the baking dish; cut into 48 squares.