Preheat the oven to 350 degrees F. Line 14 muffin tins with parchment paper liners (see notes).
Make the streusel: In a small bowl add the flour, brown sugar, butter, and cinnamon. Mix/mash with a fork until you have a crumbly mixture. Set aside.
In a large mixing bowl whisk together the melted butter, maple syrup, vanilla, buttermilk, greek yogurt, and eggs until smooth.
In a separate bowl add the flour, baking powder, baking soda, cinnamon, and salt. Mix until combined.
Add the dry ingredients to the wet ingredients and mix until just combined, making sure to not over mix.
Add your whole blueberries (or mashed - see notes) and fold until the blueberries are swirled into the batter.
Fill the muffin tins to the brim and evenly sprinkle the struesel over the batter. Transfer to the oven and bake for 25-30 minutes, or until a toothpick inserted into the center comes out clean. Enjoy the tastiest homemade muffins!