朱古力爆蛋糕 Very Chocolate Cupcake

Ingredients:
1 1/3 all-purpose flour
2/3 unsweetened cocoa powder
1/4 teaspoon baking soda
2 teaspoons baking powder
1/8 teaspoon salt
3 tablespoons butter
1 1/2 cup white sugar
2 eggs
3/4 teaspoon vanilla extract
1 cup milk