Preheat the oven to 400°F. Lightly spray a muffin pan and set aside.
In a small bowl, mix together the milk and the vinegar. Set aside to “sour”.
In a large bowl, combine the flours, sugar, baking powder and baking soda. Add in the egg, butter and “soured” milk, and mix until just combined.
Scoop half the mixture into the prepared baking pan. Sprinkle some chocolate chips on top of each (I used around 11-15 individual chocolate chips), then divide the remaining mixture over top.
Bake in the preheated oven for 25 minutes, or until muffins are browned. Allow to cool in the pan for around 5 minutes before placing them on wire racks to cool completely.
Notes
Nutrition information is an estimate. Different products and brands could alter this.