1. preheat oven to 350. in medium sauce pan melt butter and unsweetened chocolate over low heat, stir constantly.
2. Grease pan. Stir sugar int chocolate mixture in saucepan. And eggs, one at a time, stir in vanilla.
3. in small mixing bowl stir flour, and baking soda. Add to chocolate mixture. Spread batter in pan
4. Bake for 30 min. for 8-inch pans, 25 for 9-inch pans. cool in pan, on a rack.