In a double boiler, over hot water, melt chocolate. Add sugar, cream, butter and salt. Cook, stirring, until chocolate and butter are melted and sugar has dissolved, about 5 minutes. Stir in liqueur.
Pour chocolate mixture into porcelain insert of fondue pot. Set the splatter guard on top.
If fondue pot also has an outer metal pot, fill the metal pot with hot water before adding porcelain insert. Set the fondue pot on a level table and light the fuel burner, following manufacturer's directions.
Serve with chocolates squares, angel food cake, dried fruit, strawberries, bananas, mandarin oranges, apples and marshmallows.