Put 12 ounces chopped semisweet chocolate in a heatproof bowl. Bring 1 cup heavy cream, 1 tablespoon butter and a pinch of salt to a simmer in a saucepan; pour over the chocolate. Let sit until melted, then stir until smooth. Add 1/4 cup espresso and 1 teaspoon vanilla stir until smooth and shiny. Pour into a shallow baking dish and refrigerate until firm, at least 3 hours. Roll tablespoonfuls of the chocolate into about 20 balls, then roll in shredded coconut, cocoa powder or crushed peppermint candies. Refrigerate until firm, at least 1 hour.