01 - Preheat the oven to 375°F. Line a 12-cup muffin tin with paper liners or grease lightly.
02 - In a large bowl, whisk together the flour, sugar, baking powder, baking soda, and salt.
03 - In a separate bowl, beat the eggs, then whisk in the milk, melted butter, and vanilla extract.
04 - Pour the wet ingredients into the dry ingredients. Stir gently until just combined to avoid overmixing.
05 - Fold in the chocolate chips and nuts if using.
06 - Divide the batter evenly among the muffin cups, filling each about 3/4 full.
07 - Bake for 18 to 20 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs.
08 - Cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.