01 - Preheat oven to 350°F. Line a muffin tin or baking pan with parchment paper or lightly grease.
02 - In a large mixing bowl, whisk together flour, sugar, baking powder, baking soda, and salt until evenly blended.
03 - In a separate bowl, whisk milk, melted butter or oil, eggs, and vanilla extract until smooth.
04 - Pour the wet mixture into the dry ingredients and gently fold together just until combined; avoid overmixing.
05 - Fold in chocolate chips, berries, or nuts if using, ensuring even distribution.
06 - Spoon batter evenly into prepared muffin cups or baking pan.
07 - Bake for 20 to 25 minutes, or until a toothpick inserted in the center comes out clean.
08 - Remove from oven and allow to cool on a wire rack before serving.