Preheat oven to 375-degrees. Grease a 9"x13" baking dish. Set aside.
With mixer, combine flour, brown sugar, and salt. Cut in shortening with a pastry blender until it resembles the texture of coarse meal. Set aside 3/4 cup of this mixture in a small bowl to use as the topping.
Add baking powder, soda and cinnamon to the bowl and mix. Stir in milk, vinegar and egg until mixture is smooth.
Pour batter into the prepared pan and sprinkle with the reserved crumb topping.
Bake for 25 minutes, or until golden. Allow to cool in pan before cutting into 3"x2" squares. Serve warm or at room temperature.