First prepare the Chestnut purée. In a blender mix together cooked chestnuts and whipping cream. If necessary, if the consistency isn't smooth, you can add up to 4 tbsp of water to the mixture. Also, you can use store-bought chestnuts purée but homemade is always better, since you can control the taste and texture.
Mix the eggs and sugar
In a large bowl mix together eggs, canola oil, light brown sugar and vanilla essence using a hand held mixer. Mix until the mixture is pale and airy, for about a minute. Then add homemade chestnut purée and mix until well combined. Preheat the oven to 180°C / 355 °F.
In a separate bowl stir to combine flour, baking powder and a pinch of salt. Add the dry ingredients to the chestnut mixture and mix to combine. Make sure not to overwork the batter.
Pipe the doughnuts and bake
Spray a doughnut baking tin with oil (or use butter). Fill a piping bag with chestnut doughnut batter. Cut the bottom of the bag and pipe the batter into a prepared baking tin. Place in the oven and bake for 12 minutes at 180°C / 355 °F. This doughnut recipe makes 12 doughnuts, and since we only have one baking tin, we bake in batches (2 x 6 doughnuts).TipIf you don't have a piping bag at home, you can use a regular freezer bag. Cut one corner of the bag and you will have the same functionality.
Remove from the oven and prepare caramelized chestnuts topping
Remove the baking tin from the oven. While the doughnuts are still hot, remove them from the baking tin, transfer to a wire rack to cool. Meanwhile prepare the caramelized chestnut topping (optional). Place a non-stick pan over medium-high heat. Add the maple syrup and chopped cooked chestnuts. Bring to a boil and cook for approx. 5 minutes or until the maple syrup completely covers the cooked chestnuts and is thick in texture. Remove from the heat and transfer the caramelized chestnut topping to a parchment paper and let cool for about 10 minutes.
Make the chocolate glaze and serve
Melt milk chocolate and white chocolate separately in two bowls. Add the vegetable oil to each bowl and stir to combine. The chocolate should be silky, shiny and smooth. Once the doughnuts have cooled, invert the doughnut into the chocolate glaze and let the excess drip off. Optionally, sprinkle with caramelized chestnuts topping. Enjoy.