Heat the oven to 400°F and prepare a muffin tin with paper liners.
Melt the butter in a small saucepan and set it aside to cool briefly.
In a large bowl, sift all of the dry ingredients together.
In a separate medium bowl, whisk together the eggs, buttermilk, melted butter, and vanilla extract.
Make a well in the center of the dry ingredients and pour in the liquid ingredients. Then mix them together just until all of the dry ingredients are evenly moistened. (The batter will look lumpy, and that is exactly what you want.)
Fold the blueberries into the batter, working very quickly if they are frozen so they don't thaw too much and tint your batter blue.
Spoon the batter evenly into the prepared muffin tin. (An ice cream scoop is useful here.)
Bake for 20 to 30 minutes or until the muffins are golden brown.