Preheat your oven to 350°F (175°C). Line a muffin tin with paper liners or grease it lightly with cooking spray.
In a large mixing bowl, whisk together the flour, sugar, baking powder, baking soda, salt, and matcha powder until well combined.
In another bowl, mix the melted butter, eggs, vanilla extract, and milk until smooth.
Pour the wet ingredients into the dry ingredients and stir gently until just combined. Be careful not to overmix; a few lumps are okay.
If using, fold in the white chocolate chips.
Divide the batter evenly among the muffin cups, filling each about ¾ full.
Bake in the preheated oven for 18-20 minutes, or until a toothpick inserted into the center comes out clean.
Allow the muffins to cool in the pan for 5 minutes before transferring them to a wire rack to cool completely.