Preheat oven to 350 degrees F and spray 12 muffin cups with nonstick cooking spray. Wash and dice strawberries. In a large bowl fit with a mixer, combine flour, sugar, baking powder, baking soda and salt and whisk together. In a separate bowl, combine applesauce, milk, egg and vanilla extract and whisk well to combine. Pour liquid mixture slowly into flour mixture and beat on medium-low just until combined. Batter may be very liquid, this is normal. Stir in diced strawberries and chocolate chips. Pour batter 4/5 up to the top of muffin tin, making sure to scoop chocolate chips from the bottom.

Meanwhile make the streusel topping. Combine flour, both sugars and cold butter in a medium bowl. Using a pastry blender, fork or your hands, cut in butter until mixture resembles coarse crumbs. Add more flour if needed to reach coarse crumbs. Toss in mini chocolate chips.

Reserve half the streusel batter for when muffins are done baking. Sprinkle half the streusel batter on top of muffin batter. Bake in oven for 17-22 minutes. Remove from oven when an inserted knife in the center of the muffin comes out clean. Sprinkle remaining streusel topping into muffins pressing topping in.