- Preheat the oven to 350°F. Lightly grease (or line with muffin cups, and grease the muffin cups) a 12-well muffin pan.
- Beat together the butter, sugar, baking powder, salt, vanilla, and flavor (if you're using it) until fluffy.
- Beat in the eggs, then stir in the milk.
- Mix in the flour, then the chocolate chips.
- Spoon the batter into the muffin cups; they'll be quite full. Sprinkle each muffin with a little sparkling sugar.
- Bake the muffins for 30 minutes, or until a cake tester inserted into the center of one comes out without crumbs clinging to it (a little chocolate is OK!).
- Store, well-wrapped, for 3 days at room temperature, or freeze for up to a month.