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.