In small bowl, melt unsweetened and semi-sweet chocolate over pan of hot, not boiling, water; set aside.
In mixing bowl, beat butter until creamy; gradually beat in sugar, about a third at a time. Beat in eggs, one at a time. Stir in chocolate.
Combine flour, baking powder and salt; stir into batter, blending well. Stir in vanilla; fold in pecans.
Spread into buttered and floured 8" square cake pan. Bake in 350 degree oven for 25 to 30 minutes or until top is shiny and brownies pull away from sides of pan. Sprinkle with liqueur while the brownies are still warm. Let cool completely.
Icing: In mixing bowl, over pan of hot water, combine chocolate, butter and cream until chocolate and butter have melted. Remove from heat and stir until smooth. Stir in liqueur. Gradually blend in icing sugar. Beat until cool and thickened to spreading consistency. Spread over brownies.