Fill a medium saucepan halfway with water and bring it to a rolling boil. Carefully add the chestnuts, cover the pan, and boil for 20 minutes. 2.
Turn off the heat, but leave the chestnuts in the hot water.
Working in small batches, remove just 3-4 chestnuts at a time. With a sharp knife, carefully slice each one in half.
Squeeze the soft meat directly into a blender or food processor. If it's stubborn, use the handle of a small spoon to scoop it out.
Discard any chestnuts that are dark or spoiled. 3.
Once all the chestnut meat is in the blender, add the cream, milk, salt, and sugar.
Blend on high until the mixture is silky smooth, scraping down the sides of the container as needed to ensure everything is incorporated. 4.
Pour the puree into a clean saucepan or skillet.
Warm over medium-low heat, stirring occasionally, until it's piping hot. If the puree is too thick for your liking, stir in a little more milk until you reach the desired consistency. 5.
Remove from the heat, stir in the tablespoon of butter until it melts completely, and serve immediately.
