Sourdough Peanut Butter Brownies

1/4 cup shortening
2 (1 ounce) squares unsweetened chocolate
1 cup sugar
1/4 cup peanut butter
2 eggs
1/2 cup sourdough starter
1 teaspoon vanilla
1/2 cup flour
1/2 teaspoon baking powder
1/4 teaspoon baking soda
1/4 teaspoon salt

Melt shortening with chocolate over low heat. Blend in sugar and peanut butter. Add eggs, sourdough starter, and vanilla. Combine flour, baking powder, baking soda, and salt. Stir into batter. Spread in greased 9x9 baking pan. Bake at 350 degrees for 20-25 minutes or until done.