Preheat your oven to 375°F (190°C). Line a mini muffin tin with paper liners or grease it lightly.
In a large mixing bowl, whisk together the flour, baking powder, baking soda, and salt.
In another bowl, mix the melted butter and sugar until well combined. Add the eggs and vanilla extract, and mix until smooth.
Gradually add the dry ingredients to the wet ingredients, alternating with the milk. Mix until just combined. Do not overmix.
Fold in the mini chocolate chips.
Spoon the batter into the prepared muffin tin, filling each cup about ¾ full.
Bake for 12-15 minutes, or until a toothpick inserted into the center comes out clean.
Allow the muffins to cool in the tin for a few minutes, then transfer to a wire rack to cool completely.