Mix all in a bowl to form crumbles and set aside.

Whisk together eggs, buttermilk, oil, butter. Combine well.

In another bowl, combine flour, sugars and baking powder.

Add blueberries.

Pour the dry ingredients into the wet and don't over mix, but combine.

Pour into cupcake liners and sprinkle on the streusel topping.

Bake 350 for 27 mins.

(When using my mini cast iron muffin pan, I preheated the pan and they baked 35 mins.)