Preheat your oven to 425 degrees and prepare your muffin tin with liners, or grease it with non-stick cooking spray.
In a large bowl, combine the flour, baking powder, baking soda, salt, and chocolate chips and set it aside.
In another bowl, mix together the melted butter, sugar, eggs, buttermilk, and vanilla.
Add the dry ingredients to the wet mixture and use a spatula to gently fold the mixture together, just until combined. Be careful not to over-mix the batter.
Divide the batter evenly among the 12 muffin cups--they will be full to the top.
Bake at 425 degrees F for 5 minutes. Then, reduce the oven temperature to 375 degrees F and continue baking for 12-15 more minutes or until a toothpick inserted into the center of a muffin comes out clean. Be extra cautious not to over bake the muffins or they will be dry.
Remove muffins to a wire cooling rack to cool completely.
Storing Instructions: Store the muffins in a ziplock bag or a container with a lid, with a paper towel underneath and on top of them to keep them from getting soggy. Freezing Instructions: Allow to cool completely, place in a freezer-safe ziplock bag or container and freeze for up to 3 months. Thaw on your counter or warm for a few seconds in the microwave.