For the crumble: mix the melted butter with the sugar, salt and flour and set aside.
Pre-heat your oven to 425 degrees
Prepare the muffin pan with non-stick spray or foil lined baking cups.
Wash your blueberries and pull of any stems- dry on a paper towel and set aside.
In a bowl- mix together the flour, baking powder, baking soda and salt.
In another bowl mix together the melted butter, sugar, eggs, vanilla and buttermilk.
Once you have thouroughly mixed together the wet ingredients, then you can slowly start adding the dry ingredients. Be careful not to over-mix, you want to do more of a folding motion than mixing, then fold in the blueberries.
Scoop a heaping 1/2 cup into each muffin and then top each muffin with the cruble topping.
Place the muffins in your oven and then immediately turn the oven down to 375 degrees and continue baking for about 14 minutes (I like to start checking them around 10 minutes). Your muffins are done when you are able to pull out a clean toothpick from the center of the muffin.
Cool in muffin pan for 10-15 minutes before removing from pan.
Store on the countertop for 2 days or in the refridgerator for 6 days.