Truffle Tart with Espresso Sauce

Crush or grind fine chocolate wafers in food processor. Melt 6 tbsp butter and blend into crumbs. Pat into tart or pie pan. Chill until firm before filling or bake at 300 degrees for 15 minutes, cool,and fill. Filling: In a large saucepan combine the chocolate, cream, 8 tbsp butter, and liqueur (of your choice) and heat the mixture over moderately low heat, stirring until it is smooth. Remove from heat, allow to cool for 30 minutes at room temperature. Pour into cooled tart shell and refrigerate for at least 3 hours. Sauce: In a saucepan, combine cream, sugar, and remaining butter. Cook over low heat,stirring frequently, until mixture boils. Boil 5 minutes, stirring occasionally. Remove from heat. Stir in espresso grounds.