Sourdough Streusel-Filled 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

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 a greased and floured 9-inch square pan. Sprinkle batter with half of the Streusel mixture. Add remaining batter and sprinkle remaining Streusel over top. Bake at 375 degrees F for 25 to 30 minutes or until done.