4 (1 ounce) squares sweet baking chocolate
1/2 cup hot water
1 teaspoon baking soda
1 cup (2 sticks) margarine
2 cups granulated sugar
2 teaspoons vanilla extract
1 cup chopped walnuts or pecans
1 1/2 cups all-purpose flour
1/2 teaspoon salt
1 1/2 cups sourdough starter
Place chocolate in small saucepan and add hot water; bring to a boil, stirring. Add baking soda and mix well. Mixture will be foamy. Set aside until lukewarm.
In a large bowl, cream margarine and sugar together until fluffy. Add eggs and mix in thoroughly. Add vanilla extract and cooled chocolate mixture and nuts. Gradually add flour that has been sifted with salt. Lastly, add the starter. Beat well after each addition. Grease and flour a 9 x 13-inch pan and pour batter into it. Place pan in a warm spot for 30 minutes.
Preheat oven to 350 degrees F. Bake brownie for 35 to 40 minutes.