When you have a load of nice local blueberries, one feels obligated to bake with them.
If using canned blueberries, drain them in a strainer. Rinse fresh or canned blueberries with cool water, and discard any crushed ones. Do not thaw frozen blueberries. Pull off any stems from blueberries.
Mix dry ingredients in a large bowl, adding the blueberries last. Stir thoroughly to mix all ingredients.
Mix wet ingredients in a small bowl.
Pour wet ingredients over dry and mix thoroughly until all the dry is mixed and wet.
Heat the oven to 400°F. Spray just the bottoms of 12 regular-size muffin cups with the cooking spray, or line each cup with a paper baking cup.
Spoon the batter into the muffin cups, dividing batter evenly. Sprinkle evenly with the streusel topping. Bake 20 to 25 minutes or until golden brown. If baked in a sprayed pan, let stand about 5 minutes in the pan, then remove muffins from pan to a cooling rack. If baked in paper baking cups, immediately remove muffins from the pan to a cooling rack. Serve warm or cool.
WHAT IF I AM NOT GLUTEN FREE?
Start preheating your oven before you mix any ingredients. Instead of the first 2 ingredients just use plain / all-purpose flour, likewise for the streusel topping.
THIS COMES OUT TOO SWEET, WHAT CAN I DO?
In the streusel topping substitute a good quality cooking oil such as avocado oil or regular (not extra virgin) olive oil. If you use a finishing sugar or other large grain sugar you get a nice crunch on the top as well as an almost savoury edge from the fruit oil.