Streusel-Filled Sourdough Cake

1/2 cup sourdough starter
3/4 cup granulated sugar
1/2 cup shortening
1 egg
1 1/2 cups all-purpose flour
1/2 teaspoon baking powder
1/2 teaspoon salt
1/2 cup milk

Streusel:
1/2 cup brown sugar, firmly packed
2 tablespoons all-purpose flour
2 teaspoons cinnamon
2 tablespoons butter, melted
1/2 cup chopped nuts

Heat 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.