Preheat oven to 375° F. Grease mini muffin cups or line with mini muffin liners.
Whisk together 1-½ cups flour, ¾ cup sugar, salt and baking powder. Place milk into 1 cup measuring cup; add vegetable oil, the egg, vanilla extract, and enough sour cream to measure 1 cup. Mix this with flour mixture. Fold in blueberries. Fill mini muffin cups right to the top, and sprinkle with crumb topping mixture if desired.
Mix together ½ cup sugar, 2-½ Tablespoons flour, 2 Tablespoons butter, and ¾ teaspoon cinnamon. Mix with fork, and sprinkle over muffins before baking.
Bake for 15 minutes in the preheated oven, or until done. Yield: 24 mini-muffins.
*May use frozen blueberries that have been defrosted in place of fresh blueberries.