Preheat oven to 400 degrees Fahrenheit (200 degrees C). Grease muffin pan or line with muffin liners.
In a large bowl, combine 2 ¼ c flour, 1 c sugar, salt, and baking powder. Mix well.
Add the oil, egg, and milk to the flour mixture. Stir until combined.
Gently fold in blueberries.
Fill muffin cups to the top.
Make the Streusel Topping: Add ¾ c sugar, ½ c flour, ¼ c cold, cubed butter, and ½ Tbsp ground cinnamon to a medium bowl. Use a pastry cutter to blend the ingredients together.
Generously sprinkle to topping over the muffins before baking.
Bake for 20- 25 minutes until an inserted toothpick comes out clean.
Notes
After they’ve cooled, these muffins can be frozen and stored for up to 2 months.
For an even more moist muffin, buttermilk can be used in place of milk.
The white sugar in the topping mix can be replaced with an equal amount of brown sugar.