Prepare the topping by combining all ingredients and using a pastry cutter or fork to cut the butter into the sugar and flour. Cut in butter until it is pea-size and set aside.
For the muffins, whisk together the evaporated cane juice, oil, eggs and milk. In a separate bowl, blend together the flours, baking powder and salt. Add the dry ingredients into the wet and combine using a spatula. When the batter is mostly blended, add the blueberries and fold into the batter. Be careful not to over mix. Spoon the batter into greased muffin tins about ¾ full. Add the topping evenly over the muffins. Bake at 375°F for 25 minutes. Makes 12 muffins.