1Preheat oven to 350 degrees. Butter & flour a 9-inch square baking pan.
In a small, heavy saucepan, melt butter and chocolate over low heat, stirring until smooth. Cool mixture to lukewarm (I usually just set the pan in the sink in cold water for awhile).
2In large bowl with an electric mixer, beat eggs, sugar, vanilla, espresso powder and Kahlua until mixture is thick and a bit paler. Beat in cooled chocolate mixture.
3Sift together flour, baking powder and salt. Beat this mixture into the batter until just blended. Spread batter evenly in pan. Bake in middle of oven for about 35 minutes or until a toothpick comes out with crumbs sticking to it.
4Cool brownies on a wire rack for 5 minutes before cutting into squares. You may also frost them with your favorite frosting. Keep them layered between sheets of wax paper in an airtight container. Will keep for about 5 days (but they wont last that long!)