Combine brown sugar, flour, baking powder, and shortening.

Cut the mixture together until tiny crumbs appear.

Remove 3/4 cup of the crumb mixture and set aside for the topping.

Add egg, sour milk, and baking soda to the remaining crumb mixture.

Mix well to combine.

Grease a cake pan.

Pour the cake batter into the greased pan.

Sprinkle the reserved crumb topping evenly over the batter.

Bake at 350°F (175°C) for 35 minutes, or until a toothpick inserted into the center comes out clean.

Let cool slightly before serving.