Sheila Cave's Crumb topping versatile muffins

• Crumb topping versatile muffins
  
  Muffin base:
  1 1/2 cups all-purpose flour
  3/4 cup white sugar
  1/2 tsp salt
  2 tsp. baking powder
  1/3 cup vegetable oil
  1 egg
  1/3 cup milk
  1 cup (your choice) of blueberries, cooked cranberries, bananas,
  raspberries, chocolate chips, dates or any other berry of choice.
  
  Preheat oven to 400 degrees.Mix all dry ingredients, then add the oil, milk, egg and mix well until no lumps showing. Fold in the one cup choice of what your muffin will be and fill muffin cups right to the top in your pan.
  
  Crumb topping:
  1/2 cup white sugar
  1/3 cup all-purpose flour
  1/4 cup butter, melted
  1 1/2 tsp. ground cinnamon
  
  Mix together all topping ingredients with fork keeping it crumbly. Sprinkle over the top of the muffin base in the pan. Bake muffins for 20 to 25 minutes or until done.