Preheat oven to 350 degrees.
Line muffin tray with liners if desired and set aside.
In a large bowl, mash bananas and mix in eggs, vanilla, maple syrup, oil, and milk.
In medium bowl, mix together all dry ingredients. Slowly fold into the wet ingredients.
Once well, combined, fold in the blueberries.
Scoop batter into muffin tray. Filling almost to the top, this recipe makes 12 muffins.
Melt ghee and stir in maple syrup, groats, and cinnamon. Mix well and spoon onto the tops of muffins. Press them gently with the back of the spoon so that the groats stick to the batter a little bit and don't roll off of the muffins. If you want the topping to be more of a crumble, pulse the groats and cinnamon in a food processor or Ninja for a quick second before mixing with the wet ingredients.
Bake for about 25 minutes, or until muffin tops are brown and they spring back when touched. You can also use a thermometer; muffins are done at 210 degrees.