- Preheat oven to 180°C (350°F). Line a 6-count muffin tin with non-stick muffin liners - see notes below. 
- Sift the flour, baking powder, baking soda, and salt into a large mixing bowl, and stir in the sugar. 
- In another large bowl or mixing jug, add the egg, okara, and ¼ cup milk and beat until well combined. Pour in the remaining milk, oil, and vanilla and mix well. 
- Make the crumble topping. In a medium bowl, combine the sugar, flour, butter, and cinnamon and mix with a fork until crumbly. Put aside. 
- Pour the wet ingredients into the dry, add the blueberries and mix until just combined, don’t overmix the batter because the muffins will turn out tough. 
- Spoon the batter into the liners filling them level to the top of the tin. Sprinkle with the crumb topping. 
- Bake for 15 – 20 minutes or until a toothpick inserted in the center of a muffin comes out clean. 
- Remove from the oven, leave the muffins in the tin for 5 minutes then transfer to a wire rack to cool.