Combine sourdough starter, oil and egg.
Stir together dry ingredients; flour, sugar, salt, baking soda and cinnamon. Add to the sourdough mixture.
Pour dough into a greased 9-inch square pan.
With a pastry blender, mix together crumb topping ingredients. Sprinkle topping on top of batter. Bake at 350º for 35 minutes or until golden brown and toothpick inserted near the middle comes out clean.
Cool on wire rack.
Mix together icing ingredients; 1 cup powdered sugar and 1 to 2 tablespoons french vanilla coffee creamer or milk, drizzle over coffee cake.