Preheat the oven to 350 degrees Fahrenheit.
Line a muffin tray and set aside.
In a large mixing bowl, whisk together all wet ingredients until well combined.
Add in the dry ingredients, making sure to spoon and level the flours, don't scoop from the bag.
Mix together with a wooden spoon.
Fold in the blueberries.
Use a cookie scoop or spoon and spoon the batter into the lined muffin tray, filling about 3/4 of the way up.
In a small bowl, whisk together all of the ingredients for the crumble with a fork. If it seems too wet, add more flour until it looks crumbly.
Crumble on top of the muffins.
Bake for 20-25 minutes or until golden brown on top and a toothpick comes out clean. If using coconut sugar, I find they bake a bit faster than maple sugar, so check around 18 minutes. When I used maple sugar they took closer to 25, but all ovens are different so keep an eye on them! The bake time will also be shorter for fresh berries and longer for frozen.
Let cool in the tray for about 15 minutes, then transfer to a wire rack to finish cooling.