In a bowl, mix together all dry ingredients : flour, sugar, baking powder and baking soda.
In another bowl, mix the eggs and the milk together. Then, add this mix to the dry ingredients mix, and mix quickly.
Add the melted butter, mix quickly and add the chocolate chips.
Put some paper liners in a muffin mold, then fill them up to the top. Bake 15 minutes at 360°F (180°C). There you are, your muffins are ready !