"Got milk? You're gonna need it!
I first tried this out for a company Christmas party in 1991 (Los Angeles Times), and they've been a hit ever since. They've been served in San Diego, Los Angeles, Seattle, and shipped to my ex-husband when he was in the Persian Gulf.
Melt chocolate and butter in saucepan or in large microwave-safe bowl in microwave, stirring constantly. Let sit. Beat eggs, sugar, and vanilla in large mixing bowl for about 5 minutes with electric mixer, or until well-blended. Beat in chocolate mixture and Kahlua until well-blended. Then add flour and blend well.
Stir in nuts. Pour and spread into greased 9" x 13" cake pan. Bake at 375 degrees for 35 minutes or until cake tester (toothpick/knife) comes out almost clean. DON'T OVERBAKE!
Cool for 30 minutes, then cut into squares. Makes 20-30.