Chestnut cooking methods: In the microwave Cut the chestnuts in half. Transfer to a bowl and add 2 tablespoons of water so that they donu2019t dry out. Cover bowl and microwave for 5 minutes at 800 Watts. In the oven Preheat oven to 390�F / 200�C. Make a shallow incision with a small sharp knife in a crisscross manner preferably on both side. This will help the chestnuts cook quicker it will keep them from exploding and make them easier to peel. Transfer them onto a baking tray. Roast for 25-30 minutes. Boiled Press the sharp blade of a knife on the top of the chestnuts and make an incision. Repeat the same process to create a crisscross incision. Transfer to a pot and add enough water to completely cover the chestnuts. Place pot over high heat. As soon as it comes to a boil cook for 25-30 minutes. Cook the chestnuts for 20 minutes on low heat then place them into a food processor. Refill the water if necessary. Puree them well. Add water to the puree if required to get a solid paste that will be able squeeze through the piping bag. It will get more solid when cooled down but mind not to get it runny. For best results the puree should be pressed through a sieve as to not block the piping bag when making the mountain side but if we feel lucky just skip this step.