Preheat oven to 200C.
Mix all the ingredients for streusel together in a bowl with a fork until you get moist clumps.
In a large mixing bowl, whisk together flour, baking powder, baking soda, sugar, and salt.
In a measuring cup mix together oil, vanilla, buttermilk, and eggs.
Pour wet ingredients into dry ingredients and mix to just about combine and still lumpy.
Then fold in blueberries.
Do not over mix!
Fill muffin cups to 3/4 full, and crumble streusel toppings on top of muffins.
Bake for 20-25 minutes or until skewer comes out clean.
Allow to cool completely before storing.