Combine the flour, sugar, baking soda, baking powder, and salt in a mixing bowl. Stir well.
Add the chocolate chips and mix to distribute.
Pour into storage jars or containers.
Label with contents and wet ingredients needed.
When ready to bake
Preheat oven to 425°F.
In a mixing bowl, whisk together all the wet ingredients—melted and cooled butter, eggs, milk, and vanilla—until smooth.
Add the dry mix and stir just until batter forms. Don't overmix.
Spray the top and inside of each muffin cup in your pan.
Add cupcake liners to each cup. Distribute the batter evenly among the 12 muffin cups, filling them generously. Bake at 425°F for 7 minutes.
Reduce heat to 375°F and continue baking for 10-15 minutes. Test the center muffin with a toothpick—it should come out clean.
Transfer to a cooling rack for 10-15 minutes before serving.
Notes
Cool melted butter before adding to eggs. Don't overmix batter. Spray top of pan so overflow doesn't stick. Two-temperature method creates tall muffin tops. Check at 15 minutes total—ovens vary.