Use a 9" x 13" baking pan.
Note: butter must be softened.
Place all the ingredients in a bowl. Using your fingers, squish them together, rubbing them between your fingers as you go, until they are all mixed and crumbly. Set aside.
Grease the baking pan and preheat the oven to 350 degrees (F).
Combine the flour, baking powder, and salt in a bowl and stir well with a whisk or fork to combine.
Cream the sugar with the butter. Add the eggs and beat, one at a time. Alternate adding the milk and the flour mixture. Add the vanilla and beat briefly.
Stir or fold in the blueberries gently. Pour into the prepared pan. Sprinkle the top with the crumble mixture.
Bake 40 minutes or until a cake tester comes out clean.
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