Preheat your oven to 375 degrees and grease a muffin tin with butter or nonstick spray.
Beat the softened butter and sugar together in a large mixing bowl until the mixture is pale and creamy.
Add the eggs one at a time, beating well after each addition to ensure they are fully incorporated.
Stir in the vanilla extract, baking powder, and salt.
Add half of the flour and half of the milk to the bowl, stirring until just combined, then repeat with the remaining flour and milk.
Gently fold the blueberries into the batter, being careful not to crush them.
Spoon the batter evenly into the prepared muffin cups.
Mix the sugar and nutmeg together in a small bowl and sprinkle the mixture over the tops of the muffins.
Bake for 15 to 20 minutes, or until the tops are golden and a toothpick inserted into the center comes out clean.