Streusel-filled sourdough cake

1/2 cup sourdough starter3/4 cup granulated sugar1/2 cup shortening1 egg1 1/2 cups all-purpose flour1/2 teaspoon baking powder1/2 teaspoon salt1/2 cup milkStreusel1/2 cup brown sugar, firmly packed2 tablespoons all-purpose flour2 teaspoons cinnamon2 tablespoons butter, melted1/2 cup chopped nutsPreheat oven to 375 degrees F. Grease and flour a 9-inch square pan.Measure out sourdough starter.In a separate non-reactive bowl cream together sugar, shortening and egg. Add to sourdough starter along with milk, flour, baking powder and salt. Mix well. Spread half of the batter in prepared pan. Sprinkle batter with half of the Streusel mixture. Add remaining batter and sprinkle remaining Streusel over top. Bake for 25 to 30 minutes or until done.