1. Preheat oven to 325 degrees Fahrenheit. Grease a 9- x 13-inch baking pan.
2. Melt margarine and two cups chocolate chips in a small pot over low heat, stirring until smooth. Add sugar to the pot and continue to mix. Add vanilla extract, hot water, eggs, ﬂour, and baking soda, and mix well. Cool a little and stir in remaining dark and white chocolate chips.
3. Spread in baking pan and bake 45 minutes or until toothpick inserted in center comes out slightly moist. Cool.
4. Cover well and refrigerate until cold. Cut into long, narrow bars to serve.