In a large, heavy bottomed saucepan, heat the cream over medium heat until it just begins to simmer, about 5 minutes. Add the chocolate. With a wooden spoon, stir until the chocolate melts and the mixture is smooth, about 5 minutes. Add the butter and stir to melt completely. Add the liqueur and mix well. Line a baking sheet with parchment or waxed paper. Pour the chocolate into the pan, spreading it evenly with a wooden spoon. Let it cool completely, then refrigerate until it sets. Remove the chocolate from the parchment paper, break it into pieces, and put it in the bowl of an electric mixer fitted with a wire whisk. Beat at low speed for 1 minute, then increase the speed to medium and beat until it is creamy and smooth. Transfer the mixture to a pastry bag without a tip. Pipe out 1/2-ounce truffles, each about the size of a walnut, onto a sheet of parchment paper. Refrigerate the truffles for 4 hours. Use a four-prong fork to dip, then tip the truffles onto a sheet of parchment paper. Avoid touching the dipped candies while they set. If the truffles have not set in 15 minutes, then put in the refrigerator until set. After they set, put them in paper candy cups and store between sheets of parchment paper.