Beat milk, shortening and egg in a bowl. You can use an electric mixer on low speed or stir by hand in a large bowl. I usually mix the cake batter by hand with a sturdy rubber spatula.
Stir in the dry ingredients for the buckle – flour, sugar and baking powder. Stir just until flour is moistened. This will be a thick batter that appears slightly lumpy.
Gently fold in blueberries into your batter.
Pour blueberry buckle batter into a greased 8×8 pan.
In a separate bowl, mix together flour, brown sugar, sugar, cinnamon and butter with your hands to make your crumble topping. Sprinkle the buttery streusel on top of the batter.
Bake 40 to 45 minutes at 375 degrees or until topping is golden brown.
Notes
This recipe fills a 8×8 pan. If doubling the recipe, bake in a 9×13 pan and adjust cooking time accordingly.