Preheat oven to 350 degrees. Grease 13 x 9 baking pan. Either in a saucepan or in your microwave, heat butter and chocolate till melted. Once melted, transfer to a large bowl. Mix in sugar. Beat in eggs till blended. Mix in flour and vanilla. Blend in remaining ingredients. Pour mixture into greased pan. Sprinkle extra chips on top. Bake for 30 minutes or thereabouts depending upon your oven. Cool for 10 minutes and cut into squares. Enjoy!