Preheat your oven to 375°F (190°C) and line a muffin tin with paper liners.

In a large mixing bowl, whisk together 1 ½ cups of flour, ½ cup of sugar, baking soda, baking powder, and salt.

In another bowl, mix the vegetable oil, egg, vanilla extract, and milk until well combined.

Pour the wet mixture into the dry ingredients and gently fold until just combined.

Fold in the fresh blueberries gently, making sure not to break them.

In a small bowl, combine the flour, brown sugar, and cinnamon for the streusel, then mix in the melted butter until crumbly.

Divide the muffin batter into the prepared muffin tin and sprinkle the streusel topping generously over each muffin.

Place the muffin tin in the preheated oven and bake for 18-20 minutes, or until a toothpick inserted into the center comes out clean.

Allow the muffins to cool for a few minutes in the tin before transferring them to a wire rack.

Enjoy them warm!