METHOD

Sieve the flour, baking powder and salt together, keeping back 20g of the dry mix to toss with the fresh blueberries. Cream the sugar and eggs before adding the oil and then the vanilla. Alternate the wet ingredients (lemon juice, buttermilk and milk) and dry ingredients together until smooth and then fold in the blueberries. Place the mix into greased and floured muffin tray or muffin cases.  

For the crumble topping, mix all the dry ingredients together, then rub in the butter. Sprinkle the crumble over the top and cook at 200c for 20 mins.