Preheat oven to 375°F (190°C). Grease or line a 12-cavity standard muffin pan.
Whisk together the flour, sugar, cocoa powder, baking powder, baking soda, and salt. Stir in 3/4 cup (128g) of the chocolate chips.
In a separate bowl, combine the milk, oil, egg, and vanilla.
Make a well in the center of the dry ingredients mixture. Add the milk mixture, and stir just until blended.
Spoon the batter into the prepared pan, using about 3 tablespoons of batter per cup. Sprinkle the remaining 1/4 cup (42g) chocolate chips on top of the muffins.
Bake 15 to 20 minutes, or until the muffins have darkened and a pick inserted into the center comes out clean.
Notes
*You can substitute 1/3 cup unsalted butter that has been melted and slightly cooled.
Store in an airtight container at room temperature up to 3 days.