1. Preheat the oven to 375 F and line a 12-count muffin pan with liners, or spray the cavities well with nonstick spray.
2. In a large mixing bowl, whisk together the flours, baking powder, baking soda, cinnamon and salt. In another bowl, whisk together the melted butter and applesauce before adding in the eggs and maple syrup, and mixing well again. Slowly pour in the almond milk, whisking to combine. Add the dry ingredients to the wet, mixing gently with a large spoon just until there are no visible streaks of flour left.
3. Using a cookie dough scoop or a spoon, add 1 1/2 tbsp of muffin batter to the bottom of each muffin cavity. On top of the muffin batter, drop 2 tsp of Nutella on each muffin. Using a toothpick, swirl the Nutella with the muffin batter. Divide the remaining muffin batter amongst the cavities, followed by the remaining Nutella (about 1 tsp each) on top of the batter. Swirl again with a toothpick. Sprinkle the muffins with sparkling sugar (optional) and place in the oven to bake for 20-22 minutes. Check the muffins at 20 minutes with a toothpick; if there is still muffin batter on the toothpick, bake for an additional 2 minutes before checking again. Remove the muffins from the oven and allow to cool for 5 minutes in the pan before removing to a wire rack to cool completely.

Muffins can be stored at room temperature, in an airtight container for up to 3 days, or 4-5 days in the fridge. Muffins also freeze well, up to 2 months.