Preheat the oven to 375 F and butter a muffin tin.
Combine the buttermilk, melted butter, eggs, brown sugar, and vanilla. Beat together until smooth.
In a separate bowl, combine the oatmeal, flour, ground flaxmeal, baking powder, baking soda, and salt. Mix to fully combine. Add to the wet ingredients, and mix until fully incorporated.
Drop one spoonful of batter into the bottom of each muffin tin, then add a few blueberries, then cover with more batter and more blueberries. Divide the batter evenly among 12 tins.
For the crumb topping, combine the remaining flour, brown sugar, and cinnamon. Cut in the cold butter until the mixture is crumbly. Evenly distribute among the muffins.
Bake until a cake-tester comes out clean — about 13-15 minutes. Remove from the oven.
Combine the powdered sugar and milk, to make a glaze. Drizzle glaze over all of the muffins.
Enjoy!
Recipe by The Kitchen Paper at http://c02.ddd.mwp.accessdomain.com/oatmeal-flax-blueberry-muffins/