Preheat your oven to 350°F (175°C) and line a mini muffin pan with paper liners or spray with non-stick cooking spray.

In a large mixing bowl, whisk together the flour, sugar, baking powder, baking soda, and salt.

In another bowl, combine the melted butter, milk, egg, and vanilla extract, stirring until well mixed.

Pour the wet ingredients into the dry ingredients and mix until just combined. Be careful not to overmix.

Fold in the mini chocolate chips gently until evenly distributed.

Scoop the batter into the prepared mini muffin pan, filling each cup about 2/3 full.

Bake in the preheated oven for 10-12 minutes, or until a toothpick inserted into the center comes out clean.

Allow the muffins to cool in the pan for a few minutes before transferring them to a wire rack to cool completely.