In a large mixing bowl, whisk together the flour, sugar, baking powder and salt, and make a little well in the middle.
In a separate bowl or large measuring cup, whisk together the milk, egg and vanilla, then add to the dry ingredients, along with the coconut oil, stirring just enough to moisten. There will be lumps, you’ll have to come to terms with them.
With a rubber spatula or large spoon, fold the blueberries into the batter.
Line a 12-cup muffin pan with paper muffin-liners and spoon batter into each little cup, filling them about 3/4 of the way.
If doing the streusel topping, mix all ingredients and press butter into dry ingredients with fingers until the mixture is the consistency of damp sand. It’ll have little lumps. This is good. Sprinkle mixture on tops of raw muffins.
Bake for 20 – 25 minutes, or until the tops are light golden brown.
It’s imperative that you lick the batter bowl clean as you await your muffins. Trust.