Preheat the oven to 350°F (175°C) and line a mini muffin tin with paper liners.
In a medium bowl, mix together the flour, baking soda, and salt.
In a separate large bowl, cream together the melted butter and sugar until the mixture is light and fluffy. Add eggs one at a time, mixing well after each addition.
Stir in the vanilla extract and milk, then gently fold in the dry ingredients. Mix until just combined.
Spoon the batter into the prepared muffin tin, filling each cup about 2/3 full.
Bake in preheated oven for 15-20 minutes, or until a toothpick inserted into the center of a muffin comes out clean.
Allow muffins to cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.
Notes
For an added twist, try mixing in your favorite fruits or nuts into the batter before baking.