How to Make It
In a large saucepan, bring the cream to a simmer. In a large bowl, combine the chopped chocolate with the butter and salt. Pour the hot cream over the chocolate. Let stand until the chocolate and butter are melted, about 5 minutes. Whisk the ganache until smooth and shiny.
Divide the ganache into 4 bowls. To flavor it, add either the rum, peppermint oil, espresso or cardamom to each batch. Cover the ganache and refrigerate until firm, about 3 hours.
Line 3 large rimmed baking sheets with parchment paper. Using a 1-tablespoon-size ice cream scoop, drop level tablespoons of the ganache onto the baking sheets. Chill until firm, about 1 hour.
Spoon the coatings into small bowls. Moisten your hands with ice water and roll the ganache into balls, then roll in the coatings. Package the truffles in decorative bags or boxes.
Peppermint filling with powdered sugar, chocolate cookie crumbs or mint candies
Espresso filling with cinnamon-sugar, amaretti or cocoa powder-salt mixture
Rum filling with coconut, candied ginger or toffee
Cardamom filling with cinnamon-sugar, amaretti or candied ginger
Plain chocolate filling with raspberry, malt balls or peanuts