Preheat oven to 400 degrees F.  Spray twelve 3-inch muffin tins with non-stick cooking spray.  In a small bowl, make the topping by combining cinnamon, sugar and walnuts; set aside.  In a large bowl, combine flour, baking powder and salt; set aside.  In a medium bowl, cream the butter with the granulated and brown sugars until smooth.  Beat in the eggs, then add the buttermilk until blended.  Pour the wet mixture over the dry ingredients and stir until moistened.  Gently fold in wild blueberries.  Divide the batter among the muffin tins and add topping.  Bake 20 to 25 minutes. 
Makes 1 dozen muffins.
This recipe and others like it can be found in the Favorite Recipes From the Land of Wild Blueberries pamphlet put out by the Wild Blueberry Association of North America.