Heat oven to 375 degrees F. 6 muffin cups with paper liners
Stack about 8 paper towels on the counter and pour applesauce on paper towels. Spread the applesauce around in a circle almost as wide as the towels letting the towels soak up moisture from the applesauce; Let sit for about 5 minutes. You could probably do this step in a strainer, but I did it with towels.
Meanwhile, mix the flour, cocoa powder, baking soda, baking powder and salt together in a small mixing bowl.
Scrape the drained applesauce (weight should be 5 oz, volume should now be heaping ½ cup) off the towel and place it in a second mixing bowl. Stir in the brown sugar, egg, yogurt, oil and vanilla.
Pour the dry mixture into the applesauce mixture and stir a few strokes, then add the chocolate chips and stir until blended.
Divide batter equally among 6 muffin cups, filling to the top, and bake for 20-24 minutes or until a toothpick or chopstick inserted in center comes out clean.
Note: Try substituting 5 oz (heaping half cup) of pumpkin or 5 oz mashed banana for the applesauce.