Preheat oven to 350. Butter and flour a 10 inch tube pan. Mix flour, sugar, baking powder and salt in large bowl. Melt chocolate with oil, liqueur, water and coffee granules in double boiler over barely simmering water. Transfer to a large bowl and beat in egg yolks with wooden spoon until well blended. Add dry ingredients and stir until smooth. Beat egg whites in large bowl with mixer at high speed until stiff peaks form. Use a large rubber spatula to fold them into the batter. Spoon batter into prepared pan. Bake until firm to the touch and a slightly sugary crust has formed, 30 to 40 minutes. Cool cake in pan for 15 minutes. Turn out onto a wire rack to cool completely. For the frosting, beat the coffee mixture and butter into the powdered sugar until frosting is thick and spreadable. Spread over the top and sides of the cake.
Serves 10 to 12